chromium-fstatfix.patch

--- a/sandbox/linux/seccomp-bpf-helpers/baseline_policy.cc
+++ b/sandbox/linux/seccomp-bpf-helpers/baseline_policy.cc
@@ -269,6 +269,18 @@ ResultExpr EvaluateSyscallImpl(int fs_de
     return Allow();
   }
 
+#if defined(__NR_newfstatat)
+  if (sysno == __NR_newfstatat) {
+    return RewriteFstatatSIGSYS();
+  }
+#endif
+
+#if defined(__NR_fstatat64)
+  if (sysno == __NR_fstatat64) {
+    return RewriteFstatatSIGSYS();
+  }
+#endif
+
   if (SyscallSets::IsFileSystem(sysno) ||
       SyscallSets::IsCurrentDirectory(sysno)) {
     return Error(fs_denied_errno);
--- a/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
+++ b/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
@@ -6,6 +6,8 @@
 
 #include "sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h"
 
+#include <errno.h>
+#include <fcntl.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <string.h>
@@ -355,6 +357,35 @@ intptr_t SIGSYSSchedHandler(const struct
   return -ENOSYS;
 }
 
+intptr_t SIGSYSFstatatHandler(const struct arch_seccomp_data& args,
+                              void* aux) {
+  switch (args.nr) {
+#if defined(__NR_newfstatat)
+    case __NR_newfstatat:
+#endif
+#if defined(__NR_fstatat64)
+    case __NR_fstatat64:
+#endif
+#if defined(__NR_newfstatat) || defined(__NR_fstatat64)
+      if (*reinterpret_cast<const char *>(args.args[1]) == '\0'
+          && args.args[3] == static_cast<uint64_t>(AT_EMPTY_PATH)) {
+        return sandbox::sys_fstat64(static_cast<int>(args.args[0]),
+                                    reinterpret_cast<struct stat64 *>(args.args[2]));
+      } else {
+        errno = EACCES;
+        return -1;
+      }
+      break;
+#endif
+  }
+
+  CrashSIGSYS_Handler(args, aux);
+
+  // Should never be reached.
+  RAW_CHECK(false);
+  return -ENOSYS;
+}
+
 bpf_dsl::ResultExpr CrashSIGSYS() {
   return bpf_dsl::Trap(CrashSIGSYS_Handler, NULL);
 }
@@ -387,6 +418,10 @@ bpf_dsl::ResultExpr RewriteSchedSIGSYS()
   return bpf_dsl::Trap(SIGSYSSchedHandler, NULL);
 }
 
+bpf_dsl::ResultExpr RewriteFstatatSIGSYS() {
+  return bpf_dsl::Trap(SIGSYSFstatatHandler, NULL);
+}
+
 void AllocateCrashKeys() {
 #if !defined(OS_NACL_NONSFI)
   if (seccomp_crash_key)
--- a/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h
+++ b/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h
@@ -62,6 +62,10 @@ SANDBOX_EXPORT intptr_t SIGSYSPtraceFail
 // sched_setparam(), sched_setscheduler()
 SANDBOX_EXPORT intptr_t SIGSYSSchedHandler(const arch_seccomp_data& args,
                                            void* aux);
+// If the fstatat syscall is actually a disguised fstat, calls the regular fstat
+// syscall, otherwise, crashes in the same way as CrashSIGSYS_Handler.
+SANDBOX_EXPORT intptr_t SIGSYSFstatatHandler(const struct arch_seccomp_data& args, 
+                                             void* aux);
 
 // Variants of the above functions for use with bpf_dsl.
 SANDBOX_EXPORT bpf_dsl::ResultExpr CrashSIGSYS();
@@ -72,6 +76,7 @@ SANDBOX_EXPORT bpf_dsl::ResultExpr Crash
 SANDBOX_EXPORT bpf_dsl::ResultExpr CrashSIGSYSFutex();
 SANDBOX_EXPORT bpf_dsl::ResultExpr CrashSIGSYSPtrace();
 SANDBOX_EXPORT bpf_dsl::ResultExpr RewriteSchedSIGSYS();
+SANDBOX_EXPORT bpf_dsl::ResultExpr RewriteFstatatSIGSYS();
 
 // Allocates a crash key so that Seccomp information can be recorded.
 void AllocateCrashKeys();
--- a/sandbox/linux/services/syscall_wrappers.cc
+++ b/sandbox/linux/services/syscall_wrappers.cc
@@ -261,4 +261,13 @@ int sys_sigaction(int signum,
 
 #endif  // defined(MEMORY_SANITIZER)
 
+SANDBOX_EXPORT int sys_fstat64(int fd, struct stat64 *buf)
+{
+#if defined(__NR_fstat64)
+    return syscall(__NR_fstat64, fd, buf);
+#else
+    return syscall(__NR_fstat, fd, buf);
+#endif
+}
+
 }  // namespace sandbox
--- a/sandbox/linux/services/syscall_wrappers.h
+++ b/sandbox/linux/services/syscall_wrappers.h
@@ -17,6 +17,7 @@ struct sock_fprog;
 struct rlimit64;
 struct cap_hdr;
 struct cap_data;
+struct stat64;
 
 namespace sandbox {
 
@@ -84,6 +85,9 @@ SANDBOX_EXPORT int sys_sigaction(int sig
                                  const struct sigaction* act,
                                  struct sigaction* oldact);
 
+// Recent glibc rewrites fstat to fstatat.
+SANDBOX_EXPORT int sys_fstat64(int fd, struct stat64 *buf);
+
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_SERVICES_SYSCALL_WRAPPERS_H_