Initial revision

2 files changed, 1732 insertions, 0 deletions

diff --git a/chromium-ungoogled/build/patches/linux-sandbox-fix-fstatat-crash.patch b/chromium-ungoogled/build/patches/linux-sandbox-fix-fstatat-crash.patch
new file mode 100644
index 00000000..899e48e6
--- /dev/null
+++ b/chromium-ungoogled/build/patches/linux-sandbox-fix-fstatat-crash.patch
@@ -0,0 +1,348 @@
+From 60d5e803ef2a4874d29799b638754152285e0ed9 Mon Sep 17 00:00:00 2001
+From: Matthew Denton <mpdenton@chromium.org>
+Date: Wed, 21 Jul 2021 12:55:11 +0000
+Subject: [PATCH] Linux sandbox: fix fstatat() crash
+
+This is a reland of https://crrev.com/c/2801873.
+
+Glibc has started rewriting fstat(fd, stat_buf) to
+fstatat(fd, "", stat_buf, AT_EMPTY_PATH). This works because when
+AT_EMPTY_PATH is specified, and the second argument is an empty string,
+then fstatat just performs an fstat on fd like normal.
+
+Unfortunately, fstatat() also allows stat-ing arbitrary pathnames like
+with fstatat(AT_FDCWD, "/i/am/a/file", stat_buf, 0);
+The baseline policy needs to prevent this usage of fstatat() since it
+doesn't allow access to arbitrary pathnames.
+
+Sadly, if the second argument is not an empty string, AT_EMPTY_PATH is
+simply ignored by current kernels.
+
+This means fstatat() is completely unsandboxable with seccomp, since
+we *need* to verify that the second argument is the empty string, but
+we can't dereference pointers in seccomp (due to limitations of BPF,
+and the difficulty of addressing these limitations due to TOCTOU
+issues).
+
+So, this CL Traps (raises a SIGSYS via seccomp) on any fstatat syscall.
+The signal handler, which runs in the sandboxed process, checks for
+AT_EMPTY_PATH and the empty string, and then rewrites any applicable
+fstatat() back into the old-style fstat().
+
+Bug: 1164975
+Change-Id: I3df6c04c0d781eb1f181d707ccaaead779337291
+Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3042179
+Reviewed-by: Robert Sesek <rsesek@chromium.org>
+Commit-Queue: Matthew Denton <mpdenton@chromium.org>
+Cr-Commit-Position: refs/heads/master@{#903873}
+---
+ .../seccomp-bpf-helpers/baseline_policy.cc    |  8 ++++++
+ .../baseline_policy_unittest.cc               | 17 ++++++++++++-
+ .../seccomp-bpf-helpers/sigsys_handlers.cc    | 25 +++++++++++++++++++
+ .../seccomp-bpf-helpers/sigsys_handlers.h     | 14 +++++++++++
+ .../linux/syscall_broker/broker_process.cc    | 21 ++++++++++------
+ .../syscall_broker/broker_process_unittest.cc | 18 ++++++-------
+ sandbox/linux/system_headers/linux_stat.h     |  4 +++
+ 7 files changed, 89 insertions(+), 18 deletions(-)
+
+diff --git a/sandbox/linux/seccomp-bpf-helpers/baseline_policy.cc b/sandbox/linux/seccomp-bpf-helpers/baseline_policy.cc
+index f2a60bb4d7..9df0d2dbd3 100644
+--- a/sandbox/linux/seccomp-bpf-helpers/baseline_policy.cc
++++ b/sandbox/linux/seccomp-bpf-helpers/baseline_policy.cc
+@@ -20,6 +20,7 @@
+ #include "sandbox/linux/seccomp-bpf-helpers/syscall_sets.h"
+ #include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
+ #include "sandbox/linux/services/syscall_wrappers.h"
++#include "sandbox/linux/system_headers/linux_stat.h"
+ #include "sandbox/linux/system_headers/linux_syscalls.h"
+ 
+ #if !defined(SO_PEEK_OFF)
+@@ -304,6 +305,13 @@ ResultExpr EvaluateSyscallImpl(int fs_denied_errno,
+     return Allow();
+   }
+ 
++  // The fstatat syscalls are file system syscalls, which will be denied below
++  // with fs_denied_errno. However some allowed fstat syscalls are rewritten by
++  // libc implementations to fstatat syscalls, and we need to rewrite them back.
++  if (sysno == __NR_fstatat_default) {
++    return RewriteFstatatSIGSYS(fs_denied_errno);
++  }
++
+   if (SyscallSets::IsFileSystem(sysno) ||
+       SyscallSets::IsCurrentDirectory(sysno)) {
+     return Error(fs_denied_errno);
+diff --git a/sandbox/linux/seccomp-bpf-helpers/baseline_policy_unittest.cc b/sandbox/linux/seccomp-bpf-helpers/baseline_policy_unittest.cc
+index 68c29b564b..57d307e09d 100644
+--- a/sandbox/linux/seccomp-bpf-helpers/baseline_policy_unittest.cc
++++ b/sandbox/linux/seccomp-bpf-helpers/baseline_policy_unittest.cc
+@@ -51,7 +51,8 @@ namespace sandbox {
+ 
+ namespace {
+ 
+-// This also tests that read(), write() and fstat() are allowed.
++// This also tests that read(), write(), fstat(), and fstatat(.., "", ..,
++// AT_EMPTY_PATH) are allowed.
+ void TestPipeOrSocketPair(base::ScopedFD read_end, base::ScopedFD write_end) {
+   BPF_ASSERT_LE(0, read_end.get());
+   BPF_ASSERT_LE(0, write_end.get());
+@@ -60,6 +61,20 @@ void TestPipeOrSocketPair(base::ScopedFD read_end, base::ScopedFD write_end) {
+   BPF_ASSERT_EQ(0, sys_ret);
+   BPF_ASSERT(S_ISFIFO(stat_buf.st_mode) || S_ISSOCK(stat_buf.st_mode));
+ 
++  sys_ret = fstatat(read_end.get(), "", &stat_buf, AT_EMPTY_PATH);
++  BPF_ASSERT_EQ(0, sys_ret);
++  BPF_ASSERT(S_ISFIFO(stat_buf.st_mode) || S_ISSOCK(stat_buf.st_mode));
++
++  // Make sure fstatat with anything other than an empty string is denied.
++  sys_ret = fstatat(read_end.get(), "/", &stat_buf, AT_EMPTY_PATH);
++  BPF_ASSERT_EQ(sys_ret, -1);
++  BPF_ASSERT_EQ(EPERM, errno);
++
++  // Make sure fstatat without AT_EMPTY_PATH is denied.
++  sys_ret = fstatat(read_end.get(), "", &stat_buf, 0);
++  BPF_ASSERT_EQ(sys_ret, -1);
++  BPF_ASSERT_EQ(EPERM, errno);
++
+   const ssize_t kTestTransferSize = 4;
+   static const char kTestString[kTestTransferSize] = {'T', 'E', 'S', 'T'};
+   ssize_t transfered = 0;
+diff --git a/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc b/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
+index 64edbd68bd..71068a0452 100644
+--- a/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
++++ b/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
+@@ -6,6 +6,7 @@
+ 
+ #include "sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h"
+ 
++#include <fcntl.h>
+ #include <stddef.h>
+ #include <stdint.h>
+ #include <string.h>
+@@ -22,6 +23,7 @@
+ #include "sandbox/linux/seccomp-bpf/syscall.h"
+ #include "sandbox/linux/services/syscall_wrappers.h"
+ #include "sandbox/linux/system_headers/linux_seccomp.h"
++#include "sandbox/linux/system_headers/linux_stat.h"
+ #include "sandbox/linux/system_headers/linux_syscalls.h"
+ 
+ #if defined(__mips__)
+@@ -355,6 +357,24 @@ intptr_t SIGSYSSchedHandler(const struct arch_seccomp_data& args,
+   return -ENOSYS;
+ }
+ 
++intptr_t SIGSYSFstatatHandler(const struct arch_seccomp_data& args,
++                              void* fs_denied_errno) {
++  if (args.nr == __NR_fstatat_default) {
++    if (*reinterpret_cast<const char*>(args.args[1]) == '\0' &&
++        args.args[3] == static_cast<uint64_t>(AT_EMPTY_PATH)) {
++      return syscall(__NR_fstat_default, static_cast<int>(args.args[0]),
++                     reinterpret_cast<default_stat_struct*>(args.args[2]));
++    }
++    return -reinterpret_cast<intptr_t>(fs_denied_errno);
++  }
++
++  CrashSIGSYS_Handler(args, fs_denied_errno);
++
++  // Should never be reached.
++  RAW_CHECK(false);
++  return -ENOSYS;
++}
++
+ bpf_dsl::ResultExpr CrashSIGSYS() {
+   return bpf_dsl::Trap(CrashSIGSYS_Handler, NULL);
+ }
+@@ -387,6 +407,11 @@ bpf_dsl::ResultExpr RewriteSchedSIGSYS() {
+   return bpf_dsl::Trap(SIGSYSSchedHandler, NULL);
+ }
+ 
++bpf_dsl::ResultExpr RewriteFstatatSIGSYS(int fs_denied_errno) {
++  return bpf_dsl::Trap(SIGSYSFstatatHandler,
++                       reinterpret_cast<void*>(fs_denied_errno));
++}
++
+ void AllocateCrashKeys() {
+ #if !defined(OS_NACL_NONSFI)
+   if (seccomp_crash_key)
+diff --git a/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h b/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h
+index 7a958b93b2..8cd735ce15 100644
+--- a/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h
++++ b/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h
+@@ -62,6 +62,19 @@ SANDBOX_EXPORT intptr_t SIGSYSPtraceFailure(const arch_seccomp_data& args,
+ // sched_setparam(), sched_setscheduler()
+ SANDBOX_EXPORT intptr_t SIGSYSSchedHandler(const arch_seccomp_data& args,
+                                            void* aux);
++// If the fstatat() syscall is functionally equivalent to an fstat() syscall,
++// then rewrite the syscall to the equivalent fstat() syscall which can be
++// adequately sandboxed.
++// If the fstatat() is not functionally equivalent to an fstat() syscall, we
++// fail with -fs_denied_errno.
++// If the syscall is not an fstatat() at all, crash in the same way as
++// CrashSIGSYS_Handler.
++// This is necessary because glibc and musl have started rewriting fstat(fd,
++// stat_buf) as fstatat(fd, "", stat_buf, AT_EMPTY_PATH). We rewrite the latter
++// back to the former, which is actually sandboxable.
++SANDBOX_EXPORT intptr_t
++SIGSYSFstatatHandler(const struct arch_seccomp_data& args,
++                     void* fs_denied_errno);
+ 
+ // Variants of the above functions for use with bpf_dsl.
+ SANDBOX_EXPORT bpf_dsl::ResultExpr CrashSIGSYS();
+@@ -72,6 +85,7 @@ SANDBOX_EXPORT bpf_dsl::ResultExpr CrashSIGSYSKill();
+ SANDBOX_EXPORT bpf_dsl::ResultExpr CrashSIGSYSFutex();
+ SANDBOX_EXPORT bpf_dsl::ResultExpr CrashSIGSYSPtrace();
+ SANDBOX_EXPORT bpf_dsl::ResultExpr RewriteSchedSIGSYS();
++SANDBOX_EXPORT bpf_dsl::ResultExpr RewriteFstatatSIGSYS(int fs_denied_errno);
+ 
+ // Allocates a crash key so that Seccomp information can be recorded.
+ void AllocateCrashKeys();
+diff --git a/sandbox/linux/syscall_broker/broker_process.cc b/sandbox/linux/syscall_broker/broker_process.cc
+index c2176eb785..e9dad37485 100644
+--- a/sandbox/linux/syscall_broker/broker_process.cc
++++ b/sandbox/linux/syscall_broker/broker_process.cc
+@@ -113,44 +113,49 @@ bool BrokerProcess::IsSyscallAllowed(int sysno) const {
+ }
+ 
+ bool BrokerProcess::IsSyscallBrokerable(int sysno, bool fast_check) const {
++  // The syscalls unavailable on aarch64 are all blocked by Android's default
++  // seccomp policy, even on non-aarch64 architectures. I.e., the syscalls XX()
++  // with a corresponding XXat() versions are typically unavailable in aarch64
++  // and are default disabled in Android. So, we should refuse to broker them
++  // to be consistent with the platform's restrictions.
+   switch (sysno) {
+-#if !defined(__aarch64__)
++#if !defined(__aarch64__) && !defined(OS_ANDROID)
+     case __NR_access:
+ #endif
+     case __NR_faccessat:
+       return !fast_check || allowed_command_set_.test(COMMAND_ACCESS);
+ 
+-#if !defined(__aarch64__)
++#if !defined(__aarch64__) && !defined(OS_ANDROID)
+     case __NR_mkdir:
+ #endif
+     case __NR_mkdirat:
+       return !fast_check || allowed_command_set_.test(COMMAND_MKDIR);
+ 
+-#if !defined(__aarch64__)
++#if !defined(__aarch64__) && !defined(OS_ANDROID)
+     case __NR_open:
+ #endif
+     case __NR_openat:
+       return !fast_check || allowed_command_set_.test(COMMAND_OPEN);
+ 
+-#if !defined(__aarch64__)
++#if !defined(__aarch64__) && !defined(OS_ANDROID)
+     case __NR_readlink:
+ #endif
+     case __NR_readlinkat:
+       return !fast_check || allowed_command_set_.test(COMMAND_READLINK);
+ 
+-#if !defined(__aarch64__)
++#if !defined(__aarch64__) && !defined(OS_ANDROID)
+     case __NR_rename:
+ #endif
+     case __NR_renameat:
+     case __NR_renameat2:
+       return !fast_check || allowed_command_set_.test(COMMAND_RENAME);
+ 
+-#if !defined(__aarch64__)
++#if !defined(__aarch64__) && !defined(OS_ANDROID)
+     case __NR_rmdir:
+       return !fast_check || allowed_command_set_.test(COMMAND_RMDIR);
+ #endif
+ 
+-#if !defined(__aarch64__)
++#if !defined(__aarch64__) && !defined(OS_ANDROID)
+     case __NR_stat:
+     case __NR_lstat:
+ #endif
+@@ -175,7 +180,7 @@ bool BrokerProcess::IsSyscallBrokerable(int sysno, bool fast_check) const {
+       return !fast_check || allowed_command_set_.test(COMMAND_STAT);
+ #endif
+ 
+-#if !defined(__aarch64__)
++#if !defined(__aarch64__) && !defined(OS_ANDROID)
+     case __NR_unlink:
+       return !fast_check || allowed_command_set_.test(COMMAND_UNLINK);
+ #endif
+diff --git a/sandbox/linux/syscall_broker/broker_process_unittest.cc b/sandbox/linux/syscall_broker/broker_process_unittest.cc
+index c65f25a78a..f0db08d84e 100644
+--- a/sandbox/linux/syscall_broker/broker_process_unittest.cc
++++ b/sandbox/linux/syscall_broker/broker_process_unittest.cc
+@@ -1596,52 +1596,52 @@ TEST(BrokerProcess, IsSyscallAllowed) {
+   const base::flat_map<BrokerCommand, base::flat_set<int>> kSysnosForCommand = {
+       {COMMAND_ACCESS,
+        {__NR_faccessat,
+-#if defined(__NR_access)
++#if defined(__NR_access) && !defined(OS_ANDROID)
+         __NR_access
+ #endif
+        }},
+       {COMMAND_MKDIR,
+        {__NR_mkdirat,
+-#if defined(__NR_mkdir)
++#if defined(__NR_mkdir) && !defined(OS_ANDROID)
+         __NR_mkdir
+ #endif
+        }},
+       {COMMAND_OPEN,
+        {__NR_openat,
+-#if defined(__NR_open)
++#if defined(__NR_open) && !defined(OS_ANDROID)
+         __NR_open
+ #endif
+        }},
+       {COMMAND_READLINK,
+        {__NR_readlinkat,
+-#if defined(__NR_readlink)
++#if defined(__NR_readlink) && !defined(OS_ANDROID)
+         __NR_readlink
+ #endif
+        }},
+       {COMMAND_RENAME,
+        {__NR_renameat,
+-#if defined(__NR_rename)
++#if defined(__NR_rename) && !defined(OS_ANDROID)
+         __NR_rename
+ #endif
+        }},
+       {COMMAND_UNLINK,
+        {__NR_unlinkat,
+-#if defined(__NR_unlink)
++#if defined(__NR_unlink) && !defined(OS_ANDROID)
+         __NR_unlink
+ #endif
+        }},
+       {COMMAND_RMDIR,
+        {__NR_unlinkat,
+-#if defined(__NR_rmdir)
++#if defined(__NR_rmdir) && !defined(OS_ANDROID)
+         __NR_rmdir
+ #endif
+        }},
+       {COMMAND_STAT,
+        {
+-#if defined(__NR_stat)
++#if defined(__NR_stat) && !defined(OS_ANDROID)
+            __NR_stat,
+ #endif
+-#if defined(__NR_lstat)
++#if defined(__NR_lstat) && !defined(OS_ANDROID)
+            __NR_lstat,
+ #endif
+ #if defined(__NR_fstatat)
+diff --git a/sandbox/linux/system_headers/linux_stat.h b/sandbox/linux/system_headers/linux_stat.h
+index 35788eb22a..83b89efc75 100644
+--- a/sandbox/linux/system_headers/linux_stat.h
++++ b/sandbox/linux/system_headers/linux_stat.h
+@@ -157,6 +157,10 @@ struct kernel_stat {
+ };
+ #endif
+ 
++#if !defined(AT_EMPTY_PATH)
++#define AT_EMPTY_PATH 0x1000
++#endif
++
+ // On 32-bit systems, we default to the 64-bit stat struct like libc
+ // implementations do. Otherwise we default to the normal stat struct which is
+ // already 64-bit.
diff --git a/chromium-ungoogled/build/patches/linux-sandbox-syscall-broker-use-struct-kernel_stat.patch b/chromium-ungoogled/build/patches/linux-sandbox-syscall-broker-use-struct-kernel_stat.patch
new file mode 100644
index 00000000..7aa43a7a
--- /dev/null
+++ b/chromium-ungoogled/build/patches/linux-sandbox-syscall-broker-use-struct-kernel_stat.patch
@@ -0,0 +1,1384 @@
+From 4b438323d68840453b5ef826c3997568e2e0e8c7 Mon Sep 17 00:00:00 2001
+From: Matthew Denton <mpdenton@chromium.org>
+Date: Mon, 19 Jul 2021 14:03:13 +0000
+Subject: [PATCH] Reland "Reland "Linux sandbox syscall broker: use struct
+ kernel_stat""
+
+This reverts commit ff277a52ece0b216617d770f201ed66955fe70b9.
+
+Reason for revert: reland
+
+The fix included in the reland is that fstatat64() needs to be
+allowed in the broker process's seccomp policy.
+
+This CL also includes some extra tests that the kernel_stat structures
+match the layout the kernel expects.
+
+Bug: 1164975, 1199431
+Test: trogdor Chromebook successfully boots and allows login.
+
+Original change's description:
+> Revert "Reland "Linux sandbox syscall broker: use struct kernel_stat""
+>
+> This reverts commit cffbc4432af79f720ae3c75dff380b853701bd64.
+>
+> Reason for revert: https://bugs.chromium.org/p/chromium/issues/detail?id=1199431
+>
+> Original change's description:
+> > Reland "Linux sandbox syscall broker: use struct kernel_stat"
+> >
+> > This reverts commit 23030dc650cdfa22631f25bef937905f27f06a2c.
+> >
+> > Original change's description:
+> > > Revert "Linux sandbox syscall broker: use struct kernel_stat"
+> > >
+> > > This reverts commit 784b0fcd8a3ca6bcd3acb9cfd624ec9cbbac2789.
+> > >
+> > > Reason for revert: Causing failure in
+> > > Step "sandbox_linux_unittests" failing on builder "Linux ChromiumOS MSan Tests"
+> > > See crbug.com/1198480
+> > >
+> > > Original change's description:
+> > > > Linux sandbox syscall broker: use struct kernel_stat
+> > > >
+> > > > The struct stat used in libc is different (in size and field ordering)
+> > > > from the structure assumed by the Linux kernel. So, when emulating
+> > > > system calls, we need to use the struct definition the kernel expects.
+> > > >
+> > > > This CL adds linux_stat.h that includes definitions of the different
+> > > > kernel structs.
+> > > >
+> > > > Change-Id: I53cad35c2251dff0f6b7ea77528cfa58ef3cab4a
+> > > > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2780876
+> > > > Commit-Queue: Matthew Denton <mpdenton@chromium.org>
+> > > > Reviewed-by: Robert Sesek <rsesek@chromium.org>
+> > > > Cr-Commit-Position: refs/heads/master@{#871767}
+> > >
+> > > Change-Id: Icbec38f2103c8424dec79ab1870b97c3e83f9361
+> > > No-Presubmit: true
+> > > No-Tree-Checks: true
+> > > No-Try: true
+> > > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2821812
+> > > Auto-Submit: Victor Vianna <victorvianna@google.com>
+> > > Owners-Override: Victor Vianna <victorvianna@google.com>
+> > > Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
+> > > Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
+> > > Cr-Commit-Position: refs/heads/master@{#871882}
+> >
+> > Change-Id: I1f39bb5242961474def594ff7dbea52009f2cee4
+> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2824115
+> > Auto-Submit: Matthew Denton <mpdenton@chromium.org>
+> > Commit-Queue: Matthew Denton <mpdenton@chromium.org>
+> > Reviewed-by: Robert Sesek <rsesek@chromium.org>
+> > Cr-Commit-Position: refs/heads/master@{#872812}
+>
+> Fixed: 1199431
+> Change-Id: Iebfc0c48201bf22ff9c54d8d5c8a43d26a880098
+> No-Presubmit: true
+> No-Tree-Checks: true
+> No-Try: true
+> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2830459
+> Auto-Submit: Kyle Horimoto <khorimoto@chromium.org>
+> Commit-Queue: Matthew Denton <mpdenton@chromium.org>
+> Commit-Queue: Kinuko Yasuda <kinuko@chromium.org>
+> Reviewed-by: Matthew Denton <mpdenton@chromium.org>
+> Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
+> Owners-Override: Kinuko Yasuda <kinuko@chromium.org>
+> Cr-Commit-Position: refs/heads/master@{#873173}
+
+Change-Id: Ibe6a485070f33489aaa157b51b908c2d23d174d7
+Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2848936
+Reviewed-by: Robert Sesek <rsesek@chromium.org>
+Commit-Queue: Matthew Denton <mpdenton@chromium.org>
+Cr-Commit-Position: refs/heads/master@{#902981}
+---
+ sandbox/linux/BUILD.gn                        |   1 +
+ .../seccomp_broker_process_unittest.cc        |  40 +++-
+ sandbox/linux/seccomp-bpf-helpers/DEPS        |   1 -
+ ...scall_parameters_restrictions_unittests.cc |   4 -
+ sandbox/linux/services/syscall_wrappers.cc    |  50 ++++-
+ sandbox/linux/services/syscall_wrappers.h     |  15 ++
+ .../services/syscall_wrappers_unittest.cc     | 129 +++++++++++-
+ sandbox/linux/syscall_broker/DEPS             |   3 +-
+ sandbox/linux/syscall_broker/broker_client.cc |   4 +-
+ sandbox/linux/syscall_broker/broker_client.h  |   4 +-
+ sandbox/linux/syscall_broker/broker_host.cc   |  23 ++-
+ .../syscall_broker/broker_process_unittest.cc |  74 +++----
+ .../remote_syscall_arg_handler_unittest.cc    |  36 ++--
+ .../syscall_broker/syscall_dispatcher.cc      |  67 ++++---
+ .../linux/syscall_broker/syscall_dispatcher.h |  27 ++-
+ sandbox/linux/system_headers/linux_stat.h     | 188 ++++++++++++++++++
+ sandbox/linux/system_headers/linux_time.h     |  26 +++
+ sandbox/linux/tests/test_utils.cc             |  15 ++
+ sandbox/linux/tests/test_utils.h              |   2 +
+ .../policy/linux/bpf_broker_policy_linux.cc   |   4 +-
+ 20 files changed, 595 insertions(+), 118 deletions(-)
+ create mode 100644 sandbox/linux/system_headers/linux_stat.h
+
+diff --git a/sandbox/linux/BUILD.gn b/sandbox/linux/BUILD.gn
+index 2f778dd0bc..ccbbc91716 100644
+--- a/sandbox/linux/BUILD.gn
++++ b/sandbox/linux/BUILD.gn
+@@ -443,6 +443,7 @@ source_set("sandbox_services_headers") {
+     "system_headers/linux_ptrace.h",
+     "system_headers/linux_seccomp.h",
+     "system_headers/linux_signal.h",
++    "system_headers/linux_stat.h",
+     "system_headers/linux_syscalls.h",
+     "system_headers/linux_time.h",
+     "system_headers/linux_ucontext.h",
+diff --git a/sandbox/linux/integration_tests/seccomp_broker_process_unittest.cc b/sandbox/linux/integration_tests/seccomp_broker_process_unittest.cc
+index 9da9c68911..8a941983b1 100644
+--- a/sandbox/linux/integration_tests/seccomp_broker_process_unittest.cc
++++ b/sandbox/linux/integration_tests/seccomp_broker_process_unittest.cc
+@@ -34,6 +34,7 @@
+ #include "sandbox/linux/syscall_broker/broker_file_permission.h"
+ #include "sandbox/linux/syscall_broker/broker_process.h"
+ #include "sandbox/linux/system_headers/linux_seccomp.h"
++#include "sandbox/linux/system_headers/linux_stat.h"
+ #include "sandbox/linux/system_headers/linux_syscalls.h"
+ #include "sandbox/linux/tests/scoped_temporary_file.h"
+ #include "sandbox/linux/tests/test_utils.h"
+@@ -202,6 +203,26 @@ namespace {
+ // not accept this as a valid error number. E.g. bionic accepts up to 255, glibc
+ // and musl up to 4096.
+ const int kFakeErrnoSentinel = 254;
++
++void ConvertKernelStatToLibcStat(default_stat_struct& in_stat,
++                                 struct stat& out_stat) {
++  out_stat.st_dev = in_stat.st_dev;
++  out_stat.st_ino = in_stat.st_ino;
++  out_stat.st_mode = in_stat.st_mode;
++  out_stat.st_nlink = in_stat.st_nlink;
++  out_stat.st_uid = in_stat.st_uid;
++  out_stat.st_gid = in_stat.st_gid;
++  out_stat.st_rdev = in_stat.st_rdev;
++  out_stat.st_size = in_stat.st_size;
++  out_stat.st_blksize = in_stat.st_blksize;
++  out_stat.st_blocks = in_stat.st_blocks;
++  out_stat.st_atim.tv_sec = in_stat.st_atime_;
++  out_stat.st_atim.tv_nsec = in_stat.st_atime_nsec_;
++  out_stat.st_mtim.tv_sec = in_stat.st_mtime_;
++  out_stat.st_mtim.tv_nsec = in_stat.st_mtime_nsec_;
++  out_stat.st_ctim.tv_sec = in_stat.st_ctime_;
++  out_stat.st_ctim.tv_nsec = in_stat.st_ctime_nsec_;
++}
+ }  // namespace
+ 
+ // There are a variety of ways to make syscalls in a sandboxed process. One is
+@@ -217,6 +238,10 @@ class Syscaller {
+ 
+   virtual int Open(const char* filepath, int flags) = 0;
+   virtual int Access(const char* filepath, int mode) = 0;
++  // NOTE: we use struct stat instead of default_stat_struct, to make the libc
++  // syscaller simpler. Copying from default_stat_struct (the structure returned
++  // from a stat sycall) to struct stat (the structure exposed by a libc to its
++  // users) is simpler than going in the opposite direction.
+   virtual int Stat(const char* filepath,
+                    bool follow_links,
+                    struct stat* statbuf) = 0;
+@@ -243,8 +268,12 @@ class IPCSyscaller : public Syscaller {
+   int Stat(const char* filepath,
+            bool follow_links,
+            struct stat* statbuf) override {
+-    return broker_->GetBrokerClientSignalBased()->Stat(filepath, follow_links,
+-                                                       statbuf);
++    default_stat_struct buf;
++    int ret = broker_->GetBrokerClientSignalBased()->DefaultStatForTesting(
++        filepath, follow_links, &buf);
++    if (ret >= 0)
++      ConvertKernelStatToLibcStat(buf, *statbuf);
++    return ret;
+   }
+ 
+   int Rename(const char* oldpath, const char* newpath) override {
+@@ -300,10 +329,13 @@ class DirectSyscaller : public Syscaller {
+   int Stat(const char* filepath,
+            bool follow_links,
+            struct stat* statbuf) override {
+-    int ret = follow_links ? syscall(__NR_stat, filepath, statbuf)
+-                           : syscall(__NR_lstat, filepath, statbuf);
++    struct kernel_stat buf;
++    int ret = syscall(__NR_newfstatat, AT_FDCWD, filepath, &buf,
++                      follow_links ? 0 : AT_SYMLINK_NOFOLLOW);
+     if (ret < 0)
+       return -errno;
++
++    ConvertKernelStatToLibcStat(buf, *statbuf);
+     return ret;
+   }
+ 
+diff --git a/sandbox/linux/seccomp-bpf-helpers/DEPS b/sandbox/linux/seccomp-bpf-helpers/DEPS
+index 4419fd1da3..95d1bb6cbb 100644
+--- a/sandbox/linux/seccomp-bpf-helpers/DEPS
++++ b/sandbox/linux/seccomp-bpf-helpers/DEPS
+@@ -3,5 +3,4 @@ include_rules = [
+   "+sandbox/linux/seccomp-bpf",
+   "+sandbox/linux/services",
+   "+sandbox/linux/system_headers",
+-  "+third_party/lss/linux_syscall_support.h",
+ ]
+diff --git a/sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions_unittests.cc b/sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions_unittests.cc
+index 903e702eab..76c393032c 100644
+--- a/sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions_unittests.cc
++++ b/sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions_unittests.cc
+@@ -37,10 +37,6 @@
+ #include "sandbox/linux/system_headers/linux_time.h"
+ #include "sandbox/linux/tests/unit_tests.h"
+ 
+-#if !defined(OS_ANDROID)
+-#include "third_party/lss/linux_syscall_support.h"  // for MAKE_PROCESS_CPUCLOCK
+-#endif
+-
+ namespace sandbox {
+ 
+ namespace {
+diff --git a/sandbox/linux/services/syscall_wrappers.cc b/sandbox/linux/services/syscall_wrappers.cc
+index fcfd2aa129..3bec18a14e 100644
+--- a/sandbox/linux/services/syscall_wrappers.cc
++++ b/sandbox/linux/services/syscall_wrappers.cc
+@@ -4,6 +4,7 @@
+ 
+ #include "sandbox/linux/services/syscall_wrappers.h"
+ 
++#include <fcntl.h>
+ #include <pthread.h>
+ #include <sched.h>
+ #include <setjmp.h>
+@@ -14,11 +15,13 @@
+ #include <unistd.h>
+ #include <cstring>
+ 
++#include "base/check.h"
+ #include "base/compiler_specific.h"
+ #include "base/logging.h"
+ #include "build/build_config.h"
+ #include "sandbox/linux/system_headers/capability.h"
+ #include "sandbox/linux/system_headers/linux_signal.h"
++#include "sandbox/linux/system_headers/linux_stat.h"
+ #include "sandbox/linux/system_headers/linux_syscalls.h"
+ 
+ namespace sandbox {
+@@ -217,7 +220,7 @@ asm(
+ #undef STR
+ #undef XSTR
+ 
+-#endif
++#endif  // defined(ARCH_CPU_X86_FAMILY)
+ 
+ int sys_sigaction(int signum,
+                   const struct sigaction* act,
+@@ -241,7 +244,7 @@ int sys_sigaction(int signum,
+ #error "Unsupported architecture."
+ #endif
+     }
+-#endif
++#endif  // defined(ARCH_CPU_X86_FAMILY)
+   }
+ 
+   LinuxSigAction linux_oldact = {};
+@@ -259,6 +262,47 @@ int sys_sigaction(int signum,
+   return result;
+ }
+ 
+-#endif  // defined(MEMORY_SANITIZER)
++#endif  // !defined(OS_NACL_NONSFI)
++
++int sys_stat(const char* path, struct kernel_stat* stat_buf) {
++  int res;
++#if !defined(__NR_stat)
++  res = syscall(__NR_newfstatat, AT_FDCWD, path, stat_buf, 0);
++#else
++  res = syscall(__NR_stat, path, stat_buf);
++#endif
++  if (res == 0)
++    MSAN_UNPOISON(stat_buf, sizeof(*stat_buf));
++  return res;
++}
++
++int sys_lstat(const char* path, struct kernel_stat* stat_buf) {
++  int res;
++#if !defined(__NR_lstat)
++  res = syscall(__NR_newfstatat, AT_FDCWD, path, stat_buf, AT_SYMLINK_NOFOLLOW);
++#else
++  res = syscall(__NR_lstat, path, stat_buf);
++#endif
++  if (res == 0)
++    MSAN_UNPOISON(stat_buf, sizeof(*stat_buf));
++  return res;
++}
++
++int sys_fstatat64(int dirfd,
++                  const char* pathname,
++                  struct kernel_stat64* stat_buf,
++                  int flags) {
++#if defined(__NR_fstatat64)
++  int res = syscall(__NR_fstatat64, dirfd, pathname, stat_buf, flags);
++  if (res == 0)
++    MSAN_UNPOISON(stat_buf, sizeof(*stat_buf));
++  return res;
++#else  // defined(__NR_fstatat64)
++  // We should not reach here on 64-bit systems, as the *stat*64() are only
++  // necessary on 32-bit.
++  RAW_CHECK(false);
++  return -ENOSYS;
++#endif
++}
+ 
+ }  // namespace sandbox
+diff --git a/sandbox/linux/services/syscall_wrappers.h b/sandbox/linux/services/syscall_wrappers.h
+index 1975bfbd88..b55340e4a2 100644
+--- a/sandbox/linux/services/syscall_wrappers.h
++++ b/sandbox/linux/services/syscall_wrappers.h
+@@ -17,6 +17,8 @@ struct sock_fprog;
+ struct rlimit64;
+ struct cap_hdr;
+ struct cap_data;
++struct kernel_stat;
++struct kernel_stat64;
+ 
+ namespace sandbox {
+ 
+@@ -84,6 +86,19 @@ SANDBOX_EXPORT int sys_sigaction(int signum,
+                                  const struct sigaction* act,
+                                  struct sigaction* oldact);
+ 
++// Some architectures do not have stat() and lstat() syscalls. In that case,
++// these wrappers will use newfstatat(), which is available on all other
++// architectures, with the same capabilities as stat() and lstat().
++SANDBOX_EXPORT int sys_stat(const char* path, struct kernel_stat* stat_buf);
++SANDBOX_EXPORT int sys_lstat(const char* path, struct kernel_stat* stat_buf);
++
++// Takes care of unpoisoning |stat_buf| for MSAN. Check-fails if fstatat64() is
++// not a supported syscall on the current platform.
++SANDBOX_EXPORT int sys_fstatat64(int dirfd,
++                                 const char* pathname,
++                                 struct kernel_stat64* stat_buf,
++                                 int flags);
++
+ }  // namespace sandbox
+ 
+ #endif  // SANDBOX_LINUX_SERVICES_SYSCALL_WRAPPERS_H_
+diff --git a/sandbox/linux/services/syscall_wrappers_unittest.cc b/sandbox/linux/services/syscall_wrappers_unittest.cc
+index 32820f60a8..64b9cea80f 100644
+--- a/sandbox/linux/services/syscall_wrappers_unittest.cc
++++ b/sandbox/linux/services/syscall_wrappers_unittest.cc
+@@ -5,15 +5,19 @@
+ #include "sandbox/linux/services/syscall_wrappers.h"
+ 
+ #include <stdint.h>
++#include <string.h>
+ #include <sys/syscall.h>
+ #include <sys/types.h>
+ #include <sys/wait.h>
+ #include <unistd.h>
+-#include <cstring>
+ 
++#include "base/logging.h"
++#include "base/memory/page_size.h"
+ #include "base/posix/eintr_wrapper.h"
+ #include "build/build_config.h"
+ #include "sandbox/linux/system_headers/linux_signal.h"
++#include "sandbox/linux/system_headers/linux_stat.h"
++#include "sandbox/linux/tests/scoped_temporary_file.h"
+ #include "sandbox/linux/tests/test_utils.h"
+ #include "sandbox/linux/tests/unit_tests.h"
+ #include "testing/gtest/include/gtest/gtest.h"
+@@ -93,6 +97,129 @@ TEST(SyscallWrappers, LinuxSigSet) {
+             linux_sigset);
+ }
+ 
++TEST(SyscallWrappers, Stat) {
++  // Create a file to stat, with 12 bytes of data.
++  ScopedTemporaryFile tmp_file;
++  EXPECT_EQ(12, write(tmp_file.fd(), "blahblahblah", 12));
++
++  // To test we have the correct stat structures for each kernel/platform, we
++  // will right-align them on a page, with a guard page after.
++  char* two_pages = static_cast<char*>(TestUtils::MapPagesOrDie(2));
++  TestUtils::MprotectLastPageOrDie(two_pages, 2);
++  char* page1_end = two_pages + base::GetPageSize();
++
++  // First, check that calling stat with |stat_buf| pointing to the last byte on
++  // a page causes EFAULT.
++  int res = sys_stat(tmp_file.full_file_name(),
++                     reinterpret_cast<struct kernel_stat*>(page1_end - 1));
++  ASSERT_EQ(res, -1);
++  ASSERT_EQ(errno, EFAULT);
++
++  // Now, check that we have the correctly sized stat structure.
++  struct kernel_stat* sb = reinterpret_cast<struct kernel_stat*>(
++      page1_end - sizeof(struct kernel_stat));
++  // Memset to c's so we can check the kernel zero'd the padding...
++  memset(sb, 'c', sizeof(struct kernel_stat));
++  res = sys_stat(tmp_file.full_file_name(), sb);
++  ASSERT_EQ(res, 0);
++
++  // Following fields may never be consistent but should be non-zero.
++  // Don't trust the platform to define fields with any particular sign.
++  EXPECT_NE(0u, static_cast<unsigned int>(sb->st_dev));
++  EXPECT_NE(0u, static_cast<unsigned int>(sb->st_ino));
++  EXPECT_NE(0u, static_cast<unsigned int>(sb->st_mode));
++  EXPECT_NE(0u, static_cast<unsigned int>(sb->st_blksize));
++  EXPECT_NE(0u, static_cast<unsigned int>(sb->st_blocks));
++
++// We are the ones that made the file.
++// Note: normally gid and uid overflow on backwards-compatible 32-bit systems
++// and we end up with dummy uids and gids in place here.
++#if defined(ARCH_CPU_64_BITS)
++  EXPECT_EQ(geteuid(), sb->st_uid);
++  EXPECT_EQ(getegid(), sb->st_gid);
++#endif
++
++  // Wrote 12 bytes above which should fit in one block.
++  EXPECT_EQ(12u, sb->st_size);
++
++  // Can't go backwards in time, 1500000000 was some time ago.
++  EXPECT_LT(1500000000u, static_cast<unsigned int>(sb->st_atime_));
++  EXPECT_LT(1500000000u, static_cast<unsigned int>(sb->st_mtime_));
++  EXPECT_LT(1500000000u, static_cast<unsigned int>(sb->st_ctime_));
++
++  // Checking the padding for good measure.
++#if defined(__x86_64__)
++  EXPECT_EQ(0u, sb->__pad0);
++  EXPECT_EQ(0u, sb->__unused4[0]);
++  EXPECT_EQ(0u, sb->__unused4[1]);
++  EXPECT_EQ(0u, sb->__unused4[2]);
++#elif defined(__aarch64__)
++  EXPECT_EQ(0u, sb->__pad1);
++  EXPECT_EQ(0, sb->__pad2);
++  EXPECT_EQ(0u, sb->__unused4);
++  EXPECT_EQ(0u, sb->__unused5);
++#endif
++}
++
++TEST(SyscallWrappers, LStat) {
++  // Create a file to stat, with 12 bytes of data.
++  ScopedTemporaryFile tmp_file;
++  EXPECT_EQ(12, write(tmp_file.fd(), "blahblahblah", 12));
++
++  // Also create a symlink.
++  std::string symlink_name;
++  {
++    ScopedTemporaryFile tmp_file2;
++    symlink_name = tmp_file2.full_file_name();
++  }
++  int rc = symlink(tmp_file.full_file_name(), symlink_name.c_str());
++  if (rc != 0) {
++    PLOG(ERROR) << "Couldn't symlink " << symlink_name << " to target "
++                << tmp_file.full_file_name();
++    GTEST_FAIL();
++  }
++
++  struct kernel_stat lstat_info;
++  rc = sys_lstat(symlink_name.c_str(), &lstat_info);
++  if (rc < 0 && errno == EOVERFLOW) {
++    GTEST_SKIP();
++  }
++  if (rc != 0) {
++    PLOG(ERROR) << "Couldn't sys_lstat " << symlink_name;
++    GTEST_FAIL();
++  }
++
++  struct kernel_stat stat_info;
++  rc = sys_stat(symlink_name.c_str(), &stat_info);
++  if (rc < 0 && errno == EOVERFLOW) {
++    GTEST_SKIP();
++  }
++  if (rc != 0) {
++    PLOG(ERROR) << "Couldn't sys_stat " << symlink_name;
++    GTEST_FAIL();
++  }
++
++  struct kernel_stat tmp_file_stat_info;
++  rc = sys_stat(tmp_file.full_file_name(), &tmp_file_stat_info);
++  if (rc < 0 && errno == EOVERFLOW) {
++    GTEST_SKIP();
++  }
++  if (rc != 0) {
++    PLOG(ERROR) << "Couldn't sys_stat " << tmp_file.full_file_name();
++    GTEST_FAIL();
++  }
++
++  // lstat should produce information about a symlink.
++  ASSERT_TRUE(S_ISLNK(lstat_info.st_mode));
++
++  // stat-ing symlink_name and tmp_file should produce the same inode.
++  ASSERT_EQ(stat_info.st_ino, tmp_file_stat_info.st_ino);
++
++  // lstat-ing symlink_name should give a different inode than stat-ing
++  // symlink_name.
++  ASSERT_NE(stat_info.st_ino, lstat_info.st_ino);
++}
++
+ }  // namespace
+ 
+ }  // namespace sandbox
+diff --git a/sandbox/linux/syscall_broker/DEPS b/sandbox/linux/syscall_broker/DEPS
+index c477f7d363..149c463b06 100644
+--- a/sandbox/linux/syscall_broker/DEPS
++++ b/sandbox/linux/syscall_broker/DEPS
+@@ -1,4 +1,5 @@
+ include_rules = [
+-  "+sandbox/linux/system_headers",
+   "+sandbox/linux/bpf_dsl",
++  "+sandbox/linux/services",
++  "+sandbox/linux/system_headers",
+ ]
+diff --git a/sandbox/linux/syscall_broker/broker_client.cc b/sandbox/linux/syscall_broker/broker_client.cc
+index 6b1b5be433..e24f659fcf 100644
+--- a/sandbox/linux/syscall_broker/broker_client.cc
++++ b/sandbox/linux/syscall_broker/broker_client.cc
+@@ -166,7 +166,7 @@ int BrokerClient::Rmdir(const char* path) const {
+ 
+ int BrokerClient::Stat(const char* pathname,
+                        bool follow_links,
+-                       struct stat* sb) const {
++                       struct kernel_stat* sb) const {
+   if (!pathname || !sb)
+     return -EFAULT;
+ 
+@@ -181,7 +181,7 @@ int BrokerClient::Stat(const char* pathname,
+ 
+ int BrokerClient::Stat64(const char* pathname,
+                          bool follow_links,
+-                         struct stat64* sb) const {
++                         struct kernel_stat64* sb) const {
+   if (!pathname || !sb)
+     return -EFAULT;
+ 
+diff --git a/sandbox/linux/syscall_broker/broker_client.h b/sandbox/linux/syscall_broker/broker_client.h
+index 05e14c83f2..26ca78101c 100644
+--- a/sandbox/linux/syscall_broker/broker_client.h
++++ b/sandbox/linux/syscall_broker/broker_client.h
+@@ -61,10 +61,10 @@ class SANDBOX_EXPORT BrokerClient : public SyscallDispatcher {
+   int Rmdir(const char* path) const override;
+   int Stat(const char* pathname,
+            bool follow_links,
+-           struct stat* sb) const override;
++           struct kernel_stat* sb) const override;
+   int Stat64(const char* pathname,
+              bool follow_links,
+-             struct stat64* sb) const override;
++             struct kernel_stat64* sb) const override;
+   int Unlink(const char* unlink) const override;
+ 
+  private:
+diff --git a/sandbox/linux/syscall_broker/broker_host.cc b/sandbox/linux/syscall_broker/broker_host.cc
+index 1cd03a18df..1cdc01a888 100644
+--- a/sandbox/linux/syscall_broker/broker_host.cc
++++ b/sandbox/linux/syscall_broker/broker_host.cc
+@@ -20,9 +20,11 @@
+ #include "base/files/scoped_file.h"
+ #include "base/logging.h"
+ #include "base/posix/eintr_wrapper.h"
++#include "sandbox/linux/services/syscall_wrappers.h"
+ #include "sandbox/linux/syscall_broker/broker_command.h"
+ #include "sandbox/linux/syscall_broker/broker_permission_list.h"
+ #include "sandbox/linux/syscall_broker/broker_simple_message.h"
++#include "sandbox/linux/system_headers/linux_stat.h"
+ #include "sandbox/linux/system_headers/linux_syscalls.h"
+ 
+ namespace sandbox {
+@@ -193,10 +195,12 @@ void StatFileForIPC(const BrokerCommandSet& allowed_command_set,
+     RAW_CHECK(reply->AddIntToMessage(-permission_list.denied_errno()));
+     return;
+   }
++
+   if (command_type == COMMAND_STAT) {
+-    struct stat sb;
+-    int sts =
+-        follow_links ? stat(file_to_access, &sb) : lstat(file_to_access, &sb);
++    struct kernel_stat sb;
++
++    int sts = follow_links ? sandbox::sys_stat(file_to_access, &sb)
++                           : sandbox::sys_lstat(file_to_access, &sb);
+     if (sts < 0) {
+       RAW_CHECK(reply->AddIntToMessage(-errno));
+       return;
+@@ -205,10 +209,12 @@ void StatFileForIPC(const BrokerCommandSet& allowed_command_set,
+     RAW_CHECK(
+         reply->AddDataToMessage(reinterpret_cast<char*>(&sb), sizeof(sb)));
+   } else {
++#if defined(__NR_fstatat64)
+     DCHECK(command_type == COMMAND_STAT64);
+-    struct stat64 sb;
+-    int sts = follow_links ? stat64(file_to_access, &sb)
+-                           : lstat64(file_to_access, &sb);
++    struct kernel_stat64 sb;
++
++    int sts = sandbox::sys_fstatat64(AT_FDCWD, file_to_access, &sb,
++                                     follow_links ? 0 : AT_SYMLINK_NOFOLLOW);
+     if (sts < 0) {
+       RAW_CHECK(reply->AddIntToMessage(-errno));
+       return;
+@@ -216,6 +222,11 @@ void StatFileForIPC(const BrokerCommandSet& allowed_command_set,
+     RAW_CHECK(reply->AddIntToMessage(0));
+     RAW_CHECK(
+         reply->AddDataToMessage(reinterpret_cast<char*>(&sb), sizeof(sb)));
++#else  // defined(__NR_fstatat64)
++    // We should not reach here on 64-bit systems, as the *stat*64() are only
++    // necessary on 32-bit.
++    RAW_CHECK(false);
++#endif
+   }
+ }
+ 
+diff --git a/sandbox/linux/syscall_broker/broker_process_unittest.cc b/sandbox/linux/syscall_broker/broker_process_unittest.cc
+index 55ba6bccb2..c65f25a78a 100644
+--- a/sandbox/linux/syscall_broker/broker_process_unittest.cc
++++ b/sandbox/linux/syscall_broker/broker_process_unittest.cc
+@@ -811,7 +811,7 @@ void TestStatHelper(bool fast_check_in_client, bool follow_links) {
+   const char* bad_leading_path5 = "/mbogo/fictitioux";
+   const char* bad_leading_path6 = "/mbogo/fictitiousa";
+ 
+-  struct stat sb;
++  default_stat_struct sb;
+ 
+   {
+     // Actual file with permissions to see file but command not allowed.
+@@ -824,7 +824,7 @@ void TestStatHelper(bool fast_check_in_client, bool follow_links) {
+ 
+     memset(&sb, 0, sizeof(sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   tempfile_name, follow_links, &sb));
+   }
+ 
+@@ -840,7 +840,7 @@ void TestStatHelper(bool fast_check_in_client, bool follow_links) {
+ 
+     memset(&sb, 0, sizeof(sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   nonesuch_name, follow_links, &sb));
+   }
+   {
+@@ -852,7 +852,7 @@ void TestStatHelper(bool fast_check_in_client, bool follow_links) {
+ 
+     memset(&sb, 0, sizeof(sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   tempfile_name, follow_links, &sb));
+   }
+   {
+@@ -864,38 +864,39 @@ void TestStatHelper(bool fast_check_in_client, bool follow_links) {
+     ASSERT_TRUE(open_broker.Init(base::BindOnce(&NoOpCallback)));
+ 
+     memset(&sb, 0, sizeof(sb));
+-    EXPECT_EQ(-ENOENT, open_broker.GetBrokerClientSignalBased()->Stat(
+-                           nonesuch_name, follow_links, &sb));
++    EXPECT_EQ(-ENOENT,
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
++                  nonesuch_name, follow_links, &sb));
+ 
+     // Gets denied all the way back to root since no create permission.
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   leading_path1, follow_links, &sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   leading_path2, follow_links, &sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   leading_path3, follow_links, &sb));
+ 
+     // Not fooled by substrings.
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   bad_leading_path1, follow_links, &sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   bad_leading_path2, follow_links, &sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   bad_leading_path3, follow_links, &sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   bad_leading_path4, follow_links, &sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   bad_leading_path5, follow_links, &sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   bad_leading_path6, follow_links, &sb));
+   }
+   {
+@@ -907,37 +908,41 @@ void TestStatHelper(bool fast_check_in_client, bool follow_links) {
+     ASSERT_TRUE(open_broker.Init(base::BindOnce(&NoOpCallback)));
+ 
+     memset(&sb, 0, sizeof(sb));
+-    EXPECT_EQ(-ENOENT, open_broker.GetBrokerClientSignalBased()->Stat(
+-                           nonesuch_name, follow_links, &sb));
++    EXPECT_EQ(-ENOENT,
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
++                  nonesuch_name, follow_links, &sb));
+ 
+     // Gets ENOENT all the way back to root since it has create permission.
+-    EXPECT_EQ(-ENOENT, open_broker.GetBrokerClientSignalBased()->Stat(
+-                           leading_path1, follow_links, &sb));
+-    EXPECT_EQ(-ENOENT, open_broker.GetBrokerClientSignalBased()->Stat(
+-                           leading_path2, follow_links, &sb));
++    EXPECT_EQ(-ENOENT,
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
++                  leading_path1, follow_links, &sb));
++    EXPECT_EQ(-ENOENT,
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
++                  leading_path2, follow_links, &sb));
+ 
+     // But can always get the root.
+-    EXPECT_EQ(0, open_broker.GetBrokerClientSignalBased()->Stat(
+-                     leading_path3, follow_links, &sb));
++    EXPECT_EQ(0,
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
++                  leading_path3, follow_links, &sb));
+ 
+     // Not fooled by substrings.
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   bad_leading_path1, follow_links, &sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   bad_leading_path2, follow_links, &sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   bad_leading_path3, follow_links, &sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   bad_leading_path4, follow_links, &sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   bad_leading_path5, follow_links, &sb));
+     EXPECT_EQ(-kFakeErrnoSentinel,
+-              open_broker.GetBrokerClientSignalBased()->Stat(
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
+                   bad_leading_path6, follow_links, &sb));
+   }
+   {
+@@ -949,8 +954,9 @@ void TestStatHelper(bool fast_check_in_client, bool follow_links) {
+     ASSERT_TRUE(open_broker.Init(base::BindOnce(&NoOpCallback)));
+ 
+     memset(&sb, 0, sizeof(sb));
+-    EXPECT_EQ(0, open_broker.GetBrokerClientSignalBased()->Stat(
+-                     tempfile_name, follow_links, &sb));
++    EXPECT_EQ(0,
++              open_broker.GetBrokerClientSignalBased()->DefaultStatForTesting(
++                  tempfile_name, follow_links, &sb));
+ 
+     // Following fields may never be consistent but should be non-zero.
+     // Don't trust the platform to define fields with any particular sign.
+@@ -968,9 +974,9 @@ void TestStatHelper(bool fast_check_in_client, bool follow_links) {
+     EXPECT_EQ(12, sb.st_size);
+ 
+     // Can't go backwards in time, 1500000000 was some time ago.
+-    EXPECT_LT(1500000000u, static_cast<unsigned int>(sb.st_atime));
+-    EXPECT_LT(1500000000u, static_cast<unsigned int>(sb.st_mtime));
+-    EXPECT_LT(1500000000u, static_cast<unsigned int>(sb.st_ctime));
++    EXPECT_LT(1500000000u, static_cast<unsigned int>(sb.st_atime_));
++    EXPECT_LT(1500000000u, static_cast<unsigned int>(sb.st_mtime_));
++    EXPECT_LT(1500000000u, static_cast<unsigned int>(sb.st_ctime_));
+   }
+ }
+ 
+diff --git a/sandbox/linux/syscall_broker/remote_syscall_arg_handler_unittest.cc b/sandbox/linux/syscall_broker/remote_syscall_arg_handler_unittest.cc
+index fffa9bb708..f517a9867c 100644
+--- a/sandbox/linux/syscall_broker/remote_syscall_arg_handler_unittest.cc
++++ b/sandbox/linux/syscall_broker/remote_syscall_arg_handler_unittest.cc
+@@ -16,6 +16,7 @@
+ #include "base/memory/page_size.h"
+ #include "base/posix/unix_domain_socket.h"
+ #include "base/test/bind.h"
++#include "sandbox/linux/tests/test_utils.h"
+ #include "sandbox/linux/tests/unit_tests.h"
+ #include "testing/gtest/include/gtest/gtest.h"
+ 
+@@ -52,19 +53,6 @@ void VerifyCorrectString(std::string str, size_t size) {
+   }
+ }
+ 
+-void* MapPagesOrDie(size_t num_pages) {
+-  void* addr = mmap(nullptr, num_pages * base::GetPageSize(),
+-                    PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+-  PCHECK(addr);
+-  return addr;
+-}
+-
+-void MprotectLastPageOrDie(char* addr, size_t num_pages) {
+-  size_t last_page_offset = (num_pages - 1) * base::GetPageSize();
+-  PCHECK(mprotect(addr + last_page_offset, base::GetPageSize(), PROT_NONE) >=
+-         0);
+-}
+-
+ pid_t ForkWaitingChild(base::OnceCallback<void(int)>
+                            after_parent_signals_callback = base::DoNothing(),
+                        base::ScopedFD* parent_sync_fd = nullptr) {
+@@ -105,13 +93,13 @@ void ReadTest(const ReadTestConfig& test_config) {
+   size_t total_pages = (test_config.start_at + test_config.total_size +
+                         base::GetPageSize() - 1) /
+                        base::GetPageSize();
+-  char* mmap_addr = static_cast<char*>(MapPagesOrDie(total_pages));
++  char* mmap_addr = static_cast<char*>(TestUtils::MapPagesOrDie(total_pages));
+   char* addr = mmap_addr + test_config.start_at;
+   FillBufferWithPath(addr, test_config.total_size,
+                      test_config.include_null_byte);
+ 
+   if (test_config.last_page_inaccessible)
+-    MprotectLastPageOrDie(mmap_addr, total_pages);
++    TestUtils::MprotectLastPageOrDie(mmap_addr, total_pages);
+ 
+   pid_t pid = ForkWaitingChild();
+   munmap(mmap_addr, base::GetPageSize() * total_pages);
+@@ -212,7 +200,7 @@ SANDBOX_TEST(BrokerRemoteSyscallArgHandler, ReadChunkPlus1EndingOnePastPage) {
+ }
+ 
+ SANDBOX_TEST(BrokerRemoteSyscallArgHandler, ReadChildExited) {
+-  void* addr = MapPagesOrDie(1);
++  void* addr = TestUtils::MapPagesOrDie(1);
+   FillBufferWithPath(static_cast<char*>(addr), strlen(kPathPart) + 1, true);
+ 
+   base::ScopedFD parent_sync, child_sync;
+@@ -240,10 +228,10 @@ SANDBOX_TEST(BrokerRemoteSyscallArgHandler, ReadChildExited) {
+ }
+ 
+ SANDBOX_TEST(BrokerRemoteSyscallArgHandler, BasicWrite) {
+-  void* read_from = MapPagesOrDie(1);
++  void* read_from = TestUtils::MapPagesOrDie(1);
+   const size_t write_size = base::GetPageSize();
+   FillBufferWithPath(static_cast<char*>(read_from), write_size, false);
+-  char* write_to = static_cast<char*>(MapPagesOrDie(1));
++  char* write_to = static_cast<char*>(TestUtils::MapPagesOrDie(1));
+   base::ScopedFD parent_signal_fd;
+   const std::vector<int> empty_fd_vec;
+ 
+@@ -278,8 +266,8 @@ SANDBOX_TEST(BrokerRemoteSyscallArgHandler, BasicWrite) {
+ }
+ 
+ SANDBOX_TEST(BrokerRemoteSyscallArgHandler, WriteToInvalidAddress) {
+-  char* write_to = static_cast<char*>(MapPagesOrDie(1));
+-  MprotectLastPageOrDie(write_to, 1);
++  char* write_to = static_cast<char*>(TestUtils::MapPagesOrDie(1));
++  TestUtils::MprotectLastPageOrDie(write_to, 1);
+   base::ScopedFD parent_signal_fd;
+   const std::vector<int> empty_fd_vec;
+ 
+@@ -295,11 +283,11 @@ SANDBOX_TEST(BrokerRemoteSyscallArgHandler, WriteToInvalidAddress) {
+ }
+ 
+ SANDBOX_TEST(BrokerRemoteSyscallArgHandler, WritePartiallyToInvalidAddress) {
+-  char* read_from = static_cast<char*>(MapPagesOrDie(2));
++  char* read_from = static_cast<char*>(TestUtils::MapPagesOrDie(2));
+   const size_t write_size = base::GetPageSize();
+   FillBufferWithPath(static_cast<char*>(read_from), write_size, false);
+-  char* write_to = static_cast<char*>(MapPagesOrDie(2));
+-  MprotectLastPageOrDie(write_to, 2);
++  char* write_to = static_cast<char*>(TestUtils::MapPagesOrDie(2));
++  TestUtils::MprotectLastPageOrDie(write_to, 2);
+   write_to += base::GetPageSize() / 2;
+   base::ScopedFD parent_signal_fd;
+   const std::vector<int> empty_fd_vec;
+@@ -314,7 +302,7 @@ SANDBOX_TEST(BrokerRemoteSyscallArgHandler, WritePartiallyToInvalidAddress) {
+ }
+ 
+ SANDBOX_TEST(BrokerRemoteSyscallArgHandler, WriteChildExited) {
+-  char* addr = static_cast<char*>(MapPagesOrDie(1));
++  char* addr = static_cast<char*>(TestUtils::MapPagesOrDie(1));
+   FillBufferWithPath(static_cast<char*>(addr), strlen(kPathPart) + 1, true);
+ 
+   base::ScopedFD parent_sync, child_sync;
+diff --git a/sandbox/linux/syscall_broker/syscall_dispatcher.cc b/sandbox/linux/syscall_broker/syscall_dispatcher.cc
+index b9ee93c14a..8a42397ef8 100644
+--- a/sandbox/linux/syscall_broker/syscall_dispatcher.cc
++++ b/sandbox/linux/syscall_broker/syscall_dispatcher.cc
+@@ -19,8 +19,18 @@ namespace syscall_broker {
+ #define BROKER_UNPOISON_STRING(x)
+ #endif
+ 
++int SyscallDispatcher::DefaultStatForTesting(const char* pathname,
++                                             bool follow_links,
++                                             default_stat_struct* sb) {
++#if defined(__NR_fstatat64)
++  return Stat64(pathname, follow_links, sb);
++#elif defined(__NR_newfstatat)
++  return Stat(pathname, follow_links, sb);
++#endif
++}
++
+ int SyscallDispatcher::PerformStatat(const arch_seccomp_data& args,
+-                                     bool arch64) {
++                                     bool stat64) {
+   if (static_cast<int>(args.args[0]) != AT_FDCWD)
+     return -EPERM;
+   // Only allow the AT_SYMLINK_NOFOLLOW flag which is used by some libc
+@@ -30,13 +40,29 @@ int SyscallDispatcher::PerformStatat(const arch_seccomp_data& args,
+ 
+   const bool follow_links =
+       !(static_cast<int>(args.args[3]) & AT_SYMLINK_NOFOLLOW);
+-  if (arch64) {
++  if (stat64) {
+     return Stat64(reinterpret_cast<const char*>(args.args[1]), follow_links,
+-                  reinterpret_cast<struct stat64*>(args.args[2]));
++                  reinterpret_cast<struct kernel_stat64*>(args.args[2]));
+   }
+ 
+   return Stat(reinterpret_cast<const char*>(args.args[1]), follow_links,
+-              reinterpret_cast<struct stat*>(args.args[2]));
++              reinterpret_cast<struct kernel_stat*>(args.args[2]));
++}
++
++int SyscallDispatcher::PerformUnlinkat(const arch_seccomp_data& args) {
++  if (static_cast<int>(args.args[0]) != AT_FDCWD)
++    return -EPERM;
++
++  int flags = static_cast<int>(args.args[2]);
++
++  if (flags == AT_REMOVEDIR) {
++    return Rmdir(reinterpret_cast<const char*>(args.args[1]));
++  }
++
++  if (flags != 0)
++    return -EPERM;
++
++  return Unlink(reinterpret_cast<const char*>(args.args[1]));
+ }
+ 
+ int SyscallDispatcher::DispatchSyscall(const arch_seccomp_data& args) {
+@@ -127,59 +153,42 @@ int SyscallDispatcher::DispatchSyscall(const arch_seccomp_data& args) {
+ #if defined(__NR_stat)
+     case __NR_stat:
+       return Stat(reinterpret_cast<const char*>(args.args[0]), true,
+-                  reinterpret_cast<struct stat*>(args.args[1]));
++                  reinterpret_cast<struct kernel_stat*>(args.args[1]));
+ #endif
+ #if defined(__NR_stat64)
+     case __NR_stat64:
+       return Stat64(reinterpret_cast<const char*>(args.args[0]), true,
+-                    reinterpret_cast<struct stat64*>(args.args[1]));
++                    reinterpret_cast<struct kernel_stat64*>(args.args[1]));
+ #endif
+ #if defined(__NR_lstat)
+     case __NR_lstat:
+       // See https://crbug.com/847096
+       BROKER_UNPOISON_STRING(reinterpret_cast<const char*>(args.args[0]));
+       return Stat(reinterpret_cast<const char*>(args.args[0]), false,
+-                  reinterpret_cast<struct stat*>(args.args[1]));
++                  reinterpret_cast<struct kernel_stat*>(args.args[1]));
+ #endif
+ #if defined(__NR_lstat64)
+     case __NR_lstat64:
+       // See https://crbug.com/847096
+       BROKER_UNPOISON_STRING(reinterpret_cast<const char*>(args.args[0]));
+       return Stat64(reinterpret_cast<const char*>(args.args[0]), false,
+-                    reinterpret_cast<struct stat64*>(args.args[1]));
+-#endif
+-#if defined(__NR_fstatat)
+-    case __NR_fstatat:
+-      return PerformStatat(args, /*arch64=*/false);
++                    reinterpret_cast<struct kernel_stat64*>(args.args[1]));
+ #endif
+ #if defined(__NR_fstatat64)
+     case __NR_fstatat64:
+-      return PerformStatat(args, /*arch64=*/true);
++      return PerformStatat(args, /*stat64=*/true);
+ #endif
+ #if defined(__NR_newfstatat)
+     case __NR_newfstatat:
+-      return PerformStatat(args, /*arch64=*/false);
++      return PerformStatat(args, /*stat64=*/false);
+ #endif
+ #if defined(__NR_unlink)
+     case __NR_unlink:
+       return Unlink(reinterpret_cast<const char*>(args.args[0]));
+ #endif
+ #if defined(__NR_unlinkat)
+-    case __NR_unlinkat: {
+-      if (static_cast<int>(args.args[0]) != AT_FDCWD)
+-        return -EPERM;
+-
+-      int flags = static_cast<int>(args.args[2]);
+-
+-      if (flags == AT_REMOVEDIR) {
+-        return Rmdir(reinterpret_cast<const char*>(args.args[1]));
+-      }
+-
+-      if (flags != 0)
+-        return -EPERM;
+-
+-      return Unlink(reinterpret_cast<const char*>(args.args[1]));
+-    }
++    case __NR_unlinkat:
++      return PerformUnlinkat(args);
+ #endif  // defined(__NR_unlinkat)
+     default:
+       RAW_CHECK(false);
+diff --git a/sandbox/linux/syscall_broker/syscall_dispatcher.h b/sandbox/linux/syscall_broker/syscall_dispatcher.h
+index d8b8874ad9..1d6653caf3 100644
+--- a/sandbox/linux/syscall_broker/syscall_dispatcher.h
++++ b/sandbox/linux/syscall_broker/syscall_dispatcher.h
+@@ -9,13 +9,15 @@
+ #include <cstddef>
+ 
+ #include "sandbox/linux/system_headers/linux_seccomp.h"
++#include "sandbox/linux/system_headers/linux_stat.h"
++#include "sandbox/sandbox_export.h"
+ 
+ namespace sandbox {
+ namespace syscall_broker {
+ 
+ // An abstract class that defines all the system calls we perform for the
+ // sandboxed process.
+-class SyscallDispatcher {
++class SANDBOX_EXPORT SyscallDispatcher {
+  public:
+   // Emulates access()/faccessat().
+   // X_OK will always return an error in practice since the broker process
+@@ -40,19 +42,34 @@ class SyscallDispatcher {
+   virtual int Rmdir(const char* path) const = 0;
+ 
+   // Emulates stat()/stat64()/lstat()/lstat64()/fstatat()/newfstatat().
++  // Stat64 is only available on 32-bit systems.
+   virtual int Stat(const char* pathname,
+                    bool follow_links,
+-                   struct stat* sb) const = 0;
++                   struct kernel_stat* sb) const = 0;
+   virtual int Stat64(const char* pathname,
+                      bool follow_links,
+-                     struct stat64* sb) const = 0;
++                     struct kernel_stat64* sb) const = 0;
+ 
+   // Emulates unlink()/unlinkat().
+   virtual int Unlink(const char* unlink) const = 0;
+ 
++  // Different architectures use a different syscall from the stat family by
++  // default in glibc. E.g. 32-bit systems use *stat*64() and fill out struct
++  // kernel_stat64, whereas 64-bit systems use *stat*() and fill out struct
++  // kernel_stat. Some tests want to call the SyscallDispatcher directly, and
++  // should be using the default stat in order to test against glibc.
++  int DefaultStatForTesting(const char* pathname,
++                            bool follow_links,
++                            default_stat_struct* sb);
++
+   // Validates the args passed to a *statat*() syscall and performs the syscall
+-  // using Stat() or Stat64().
+-  int PerformStatat(const arch_seccomp_data& args, bool arch64);
++  // using Stat(), or on 32-bit systems it uses Stat64() for the *statat64()
++  // syscalls.
++  int PerformStatat(const arch_seccomp_data& args, bool stat64);
++
++  // Validates the args passed to an unlinkat() syscall and performs the syscall
++  // using either Unlink() or Rmdir().
++  int PerformUnlinkat(const arch_seccomp_data& args);
+ 
+   // Reads the syscall number and arguments, imposes some policy (e.g. the *at()
+   // system calls must only allow AT_FDCWD as the first argument), and
+diff --git a/sandbox/linux/system_headers/linux_stat.h b/sandbox/linux/system_headers/linux_stat.h
+new file mode 100644
+index 0000000000..35788eb22a
+--- /dev/null
++++ b/sandbox/linux/system_headers/linux_stat.h
+@@ -0,0 +1,188 @@
++// Copyright 2021 The Chromium Authors. All rights reserved.
++// Use of this source code is governed by a BSD-style license that can be
++// found in the LICENSE file.
++
++#ifndef SANDBOX_LINUX_SYSTEM_HEADERS_LINUX_STAT_H_
++#define SANDBOX_LINUX_SYSTEM_HEADERS_LINUX_STAT_H_
++
++#include <stdint.h>
++
++#include "build/build_config.h"
++#include "sandbox/linux/system_headers/linux_syscalls.h"
++
++#if defined(ARCH_CPU_MIPS_FAMILY)
++#if defined(ARCH_CPU_64_BITS)
++struct kernel_stat {
++#else
++struct kernel_stat64 {
++#endif
++  unsigned st_dev;
++  unsigned __pad0[3];
++  unsigned long long st_ino;
++  unsigned st_mode;
++  unsigned st_nlink;
++  unsigned st_uid;
++  unsigned st_gid;
++  unsigned st_rdev;
++  unsigned __pad1[3];
++  long long st_size;
++  unsigned st_atime_;
++  unsigned st_atime_nsec_;
++  unsigned st_mtime_;
++  unsigned st_mtime_nsec_;
++  unsigned st_ctime_;
++  unsigned st_ctime_nsec_;
++  unsigned st_blksize;
++  unsigned __pad2;
++  unsigned long long st_blocks;
++};
++#else
++struct kernel_stat64 {
++  unsigned long long st_dev;
++  unsigned char __pad0[4];
++  unsigned __st_ino;
++  unsigned st_mode;
++  unsigned st_nlink;
++  unsigned st_uid;
++  unsigned st_gid;
++  unsigned long long st_rdev;
++  unsigned char __pad3[4];
++  long long st_size;
++  unsigned st_blksize;
++  unsigned long long st_blocks;
++  unsigned st_atime_;
++  unsigned st_atime_nsec_;
++  unsigned st_mtime_;
++  unsigned st_mtime_nsec_;
++  unsigned st_ctime_;
++  unsigned st_ctime_nsec_;
++  unsigned long long st_ino;
++};
++#endif
++
++#if defined(__i386__) || defined(__ARM_ARCH_3__) || defined(__ARM_EABI__)
++struct kernel_stat {
++  /* The kernel headers suggest that st_dev and st_rdev should be 32bit
++   * quantities encoding 12bit major and 20bit minor numbers in an interleaved
++   * format. In reality, we do not see useful data in the top bits. So,
++   * we'll leave the padding in here, until we find a better solution.
++   */
++  unsigned short st_dev;
++  short pad1;
++  unsigned st_ino;
++  unsigned short st_mode;
++  unsigned short st_nlink;
++  unsigned short st_uid;
++  unsigned short st_gid;
++  unsigned short st_rdev;
++  short pad2;
++  unsigned st_size;
++  unsigned st_blksize;
++  unsigned st_blocks;
++  unsigned st_atime_;
++  unsigned st_atime_nsec_;
++  unsigned st_mtime_;
++  unsigned st_mtime_nsec_;
++  unsigned st_ctime_;
++  unsigned st_ctime_nsec_;
++  unsigned __unused4;
++  unsigned __unused5;
++};
++#elif defined(__x86_64__)
++struct kernel_stat {
++  uint64_t st_dev;
++  uint64_t st_ino;
++  uint64_t st_nlink;
++  unsigned st_mode;
++  unsigned st_uid;
++  unsigned st_gid;
++  unsigned __pad0;
++  uint64_t st_rdev;
++  int64_t st_size;
++  int64_t st_blksize;
++  int64_t st_blocks;
++  uint64_t st_atime_;
++  uint64_t st_atime_nsec_;
++  uint64_t st_mtime_;
++  uint64_t st_mtime_nsec_;
++  uint64_t st_ctime_;
++  uint64_t st_ctime_nsec_;
++  int64_t __unused4[3];
++};
++#elif (defined(ARCH_CPU_MIPS_FAMILY) && defined(ARCH_CPU_32_BITS))
++struct kernel_stat {
++  unsigned st_dev;
++  int st_pad1[3];
++  unsigned st_ino;
++  unsigned st_mode;
++  unsigned st_nlink;
++  unsigned st_uid;
++  unsigned st_gid;
++  unsigned st_rdev;
++  int st_pad2[2];
++  long st_size;
++  int st_pad3;
++  long st_atime_;
++  long st_atime_nsec_;
++  long st_mtime_;
++  long st_mtime_nsec_;
++  long st_ctime_;
++  long st_ctime_nsec_;
++  int st_blksize;
++  int st_blocks;
++  int st_pad4[14];
++};
++#elif defined(__aarch64__)
++struct kernel_stat {
++  unsigned long st_dev;
++  unsigned long st_ino;
++  unsigned int st_mode;
++  unsigned int st_nlink;
++  unsigned int st_uid;
++  unsigned int st_gid;
++  unsigned long st_rdev;
++  unsigned long __pad1;
++  long st_size;
++  int st_blksize;
++  int __pad2;
++  long st_blocks;
++  long st_atime_;
++  unsigned long st_atime_nsec_;
++  long st_mtime_;
++  unsigned long st_mtime_nsec_;
++  long st_ctime_;
++  unsigned long st_ctime_nsec_;
++  unsigned int __unused4;
++  unsigned int __unused5;
++};
++#endif
++
++// On 32-bit systems, we default to the 64-bit stat struct like libc
++// implementations do. Otherwise we default to the normal stat struct which is
++// already 64-bit.
++// These defines make it easy to call the right syscall to fill out a 64-bit
++// stat struct, which is the default in libc implementations but requires
++// different syscall names on 32 and 64-bit platforms.
++#if defined(__NR_fstatat64)
++
++namespace sandbox {
++using default_stat_struct = struct kernel_stat64;
++}  // namespace sandbox
++
++#define __NR_fstatat_default __NR_fstatat64
++#define __NR_fstat_default __NR_fstat64
++
++#elif defined(__NR_newfstatat)
++
++namespace sandbox {
++using default_stat_struct = struct kernel_stat;
++}  // namespace sandbox
++
++#define __NR_fstatat_default __NR_newfstatat
++#define __NR_fstat_default __NR_fstat
++
++#else
++#error "one of fstatat64 and newfstatat must be defined"
++#endif
++
++#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_LINUX_STAT_H_
+diff --git a/sandbox/linux/system_headers/linux_time.h b/sandbox/linux/system_headers/linux_time.h
+index 780f24dddd..f18c806611 100644
+--- a/sandbox/linux/system_headers/linux_time.h
++++ b/sandbox/linux/system_headers/linux_time.h
+@@ -11,6 +11,32 @@
+ #define CPUCLOCK_CLOCK_MASK 3
+ #endif
+ 
++#if !defined(CPUCLOCK_PROF)
++#define CPUCLOCK_PROF 0
++#endif
++
++#if !defined(CPUCLOCK_VIRT)
++#define CPUCLOCK_VIRT 1
++#endif
++
++#if !defined(CPUCLOCK_SCHED)
++#define CPUCLOCK_SCHED 2
++#endif
++
++#if !defined(CPUCLOCK_PERTHREAD_MASK)
++#define CPUCLOCK_PERTHREAD_MASK 4
++#endif
++
++#if !defined(MAKE_PROCESS_CPUCLOCK)
++#define MAKE_PROCESS_CPUCLOCK(pid, clock) \
++  ((int)(~(unsigned)(pid) << 3) | (int)(clock))
++#endif
++
++#if !defined(MAKE_THREAD_CPUCLOCK)
++#define MAKE_THREAD_CPUCLOCK(tid, clock) \
++  ((int)(~(unsigned)(tid) << 3) | (int)((clock) | CPUCLOCK_PERTHREAD_MASK))
++#endif
++
+ #if !defined(CLOCKFD)
+ #define CLOCKFD 3
+ #endif
+diff --git a/sandbox/linux/tests/test_utils.cc b/sandbox/linux/tests/test_utils.cc
+index 847c20b20c..cf6041a4b4 100644
+--- a/sandbox/linux/tests/test_utils.cc
++++ b/sandbox/linux/tests/test_utils.cc
+@@ -5,12 +5,14 @@
+ #include "sandbox/linux/tests/test_utils.h"
+ 
+ #include <errno.h>
++#include <sys/mman.h>
+ #include <sys/stat.h>
+ #include <sys/types.h>
+ #include <sys/wait.h>
+ #include <unistd.h>
+ 
+ #include "base/check_op.h"
++#include "base/memory/page_size.h"
+ #include "base/posix/eintr_wrapper.h"
+ 
+ namespace sandbox {
+@@ -39,4 +41,17 @@ void TestUtils::HandlePostForkReturn(pid_t pid) {
+   }
+ }
+ 
++void* TestUtils::MapPagesOrDie(size_t num_pages) {
++  void* addr = mmap(nullptr, num_pages * base::GetPageSize(),
++                    PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
++  PCHECK(addr);
++  return addr;
++}
++
++void TestUtils::MprotectLastPageOrDie(char* addr, size_t num_pages) {
++  size_t last_page_offset = (num_pages - 1) * base::GetPageSize();
++  PCHECK(mprotect(addr + last_page_offset, base::GetPageSize(), PROT_NONE) >=
++         0);
++}
++
+ }  // namespace sandbox
+diff --git a/sandbox/linux/tests/test_utils.h b/sandbox/linux/tests/test_utils.h
+index 7cf9749fe4..43b028b1e3 100644
+--- a/sandbox/linux/tests/test_utils.h
++++ b/sandbox/linux/tests/test_utils.h
+@@ -19,6 +19,8 @@ class TestUtils {
+   // makes sure that if fork() succeeded the child exits
+   // and the parent waits for it.
+   static void HandlePostForkReturn(pid_t pid);
++  static void* MapPagesOrDie(size_t num_pages);
++  static void MprotectLastPageOrDie(char* addr, size_t num_pages);
+ 
+  private:
+   DISALLOW_IMPLICIT_CONSTRUCTORS(TestUtils);
+diff --git a/sandbox/policy/linux/bpf_broker_policy_linux.cc b/sandbox/policy/linux/bpf_broker_policy_linux.cc
+index 2963bb9ca8..6dc8c0581b 100644
+--- a/sandbox/policy/linux/bpf_broker_policy_linux.cc
++++ b/sandbox/policy/linux/bpf_broker_policy_linux.cc
+@@ -93,8 +93,8 @@ ResultExpr BrokerProcessPolicy::EvaluateSyscall(int sysno) const {
+         return Allow();
+       break;
+ #endif
+-#if defined(__NR_fstatat)
+-    case __NR_fstatat:
++#if defined(__NR_fstatat64)
++    case __NR_fstatat64:
+       if (allowed_command_set_.test(syscall_broker::COMMAND_STAT))
+         return Allow();
+       break;