# HG changeset patch
# User Jed Davis <jld@mozilla.com>
# Date 1598606638 0
# Node ID a65fc6aca1f2337cb5e8e69f50b539d3c0de95ab
# Parent  a6c226548fa02c3ac4681499103cd85217c6de07
Bug 1660901 - Support the fstat-like subset of fstatat in the Linux sandbox policies. r=gcp, a=RyanVM

Differential Revision: https://phabricator.services.mozilla.com/D88499

diff --git a/security/sandbox/linux/SandboxFilter.cpp b/security/sandbox/linux/SandboxFilter.cpp
--- a/security/sandbox/linux/SandboxFilter.cpp
+++ b/security/sandbox/linux/SandboxFilter.cpp
@@ -238,16 +238,22 @@ class SandboxPolicyCommon : public Sandb
   }
 
   static intptr_t StatAtTrap(ArgsRef aArgs, void* aux) {
     auto broker = static_cast<SandboxBrokerClient*>(aux);
     auto fd = static_cast<int>(aArgs.args[0]);
     auto path = reinterpret_cast<const char*>(aArgs.args[1]);
     auto buf = reinterpret_cast<statstruct*>(aArgs.args[2]);
     auto flags = static_cast<int>(aArgs.args[3]);
+
+    if (fd != AT_FDCWD && (flags & AT_EMPTY_PATH) != 0 &&
+        strcmp(path, "") == 0) {
+      return ConvertError(fstatsyscall(fd, buf));
+    }
+
     if (fd != AT_FDCWD && path[0] != '/') {
       SANDBOX_LOG_ERROR("unsupported fd-relative fstatat(%d, \"%s\", %p, %d)",
                         fd, path, buf, flags);
       return BlockedSyscallTrap(aArgs, nullptr);
     }
     if ((flags & ~AT_SYMLINK_NOFOLLOW) != 0) {
       SANDBOX_LOG_ERROR("unsupported flags %d in fstatat(%d, \"%s\", %p, %d)",
                         (flags & ~AT_SYMLINK_NOFOLLOW), fd, path, buf, flags);
diff --git a/security/sandbox/linux/broker/SandboxBrokerUtils.h b/security/sandbox/linux/broker/SandboxBrokerUtils.h
--- a/security/sandbox/linux/broker/SandboxBrokerUtils.h
+++ b/security/sandbox/linux/broker/SandboxBrokerUtils.h
@@ -14,17 +14,19 @@
 // On 32-bit Linux, stat calls are translated by libc into stat64
 // calls. We'll intercept those and handle them in the stat functions
 // but must be sure to use the right structure layout.
 
 #if defined(__NR_stat64)
 typedef struct stat64 statstruct;
 #  define statsyscall stat64
 #  define lstatsyscall lstat64
+#  define fstatsyscall fstat64
 #elif defined(__NR_stat)
 typedef struct stat statstruct;
 #  define statsyscall stat
 #  define lstatsyscall lstat
+#  define fstatsyscall fstat
 #else
 #  error Missing stat syscall include.
 #endif
 
 #endif  // mozilla_SandboxBrokerUtils_h