Reland "Skip stale filehandle in proc_util.cc"

This reverts commit ebfd5a5979.

Reason for revert: Initializing the "uninitialized" variable

Original change's description:
> Revert "Skip stale filehandle in proc_util.cc"
>
> This reverts commit dc1fb3ffda.
>
> Reason for revert:
> LUCI Bisection has identified this change as the cause of a test failure. See the analysis: https://ci.chromium.org/ui/p/chromium/bisection/test-analysis/b/5091314988220416
>
> Sample build with failed test: https://ci.chromium.org/b/8724836128577596785
> Affected test(s):
> [ninja://chrome/test:browser_tests/OpticalCharacterRecognizerTest.PerformOCR_PdfMetrics/All.OCR_Enabled_Library_Available](https://ci.chromium.org/ui/test/chromium/ninja:%2F%2Fchrome%2Ftest:browser_tests%2FOpticalCharacterRecognizerTest.PerformOCR_PdfMetrics%2FAll.OCR_Enabled_Library_Available?q=VHash%3A15e8c90d55ca90bb)
>
> If this is a false positive, please report it at http://b.corp.google.com/createIssue?component=1199205&description=Analysis%3A+https%3A%2F%2Fci.chromium.org%2Fui%2Fp%2Fchromium%2Fbisection%2Ftest-analysis%2Fb%2F5091314988220416&format=PLAIN&priority=P3&title=Wrongly+blamed+https%3A%2F%2Fchromium-review.googlesource.com%2Fc%2Fchromium%2Fsrc%2F%2B%2F5973241&type=BUG
>
> Original change's description:
> > Skip stale filehandle in proc_util.cc
> >
> > This fixes a crash in the sandbox when running tests in Cider.
> >
> > Also remove the is_cog() function from test_env.py, as it is no
> > longer needed.
> >
> > Bug: 362595425, 347350045
> > Change-Id: I63d28d2f0fbf39ba0d22be7ac88e140768f33171
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5973241
> > Reviewed-by: Ben Pastene <bpastene@chromium.org>
> > Commit-Queue: Gary Tong <gatong@chromium.org>
> > Reviewed-by: Matthew Denton <mpdenton@chromium.org>
> > Cr-Commit-Position: refs/heads/main@{#1411004}
> >
>
> Bug: 362595425, 347350045
> Change-Id: I2ef44348b968254882c258ced25a928a3cb5c85f
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6199173
> Reviewed-by: Ben Pastene <bpastene@chromium.org>
> Commit-Queue: Gary Tong <gatong@chromium.org>
> Reviewed-by: Matthew Denton <mpdenton@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1411450}

Bug: 362595425, 347350045
Change-Id: Idc480fb3b34c9637e26a458ced5dbac2175e2115
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6207410
Reviewed-by: Matthew Denton <mpdenton@chromium.org>
Commit-Queue: Gregory Guterman <guterman@google.com>
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1412549}

sandbox/linux/services/proc_util.cc

@@ -94,7 +94,19 @@ bool ProcUtil::HasOpenDirectory(int proc_fd) {
 
     struct stat s;
     // It's OK to use proc_self_fd here, fstatat won't modify it.
-    PCHECK(fstatat(proc_self_fd, de->d_name, &s, 0) == 0);
+    int stat_res = fstatat(proc_self_fd, de->d_name, &s, 0);
+    // Check for stale symlinks and skip them if they meet certain criteria.
+    // See crbug.com/362595425
+    char filename[PATH_MAX] = {};  // Initialize for robustness
+    if (stat_res == -1 && errno == ESTALE && de->d_type == DT_LNK &&
+        readlinkat(proc_self_fd, de->d_name, filename, sizeof(filename)) !=
+            -1) {
+      static constexpr std::string_view kStalePrefix = "/google/cog/";
+      if (strncmp(filename, kStalePrefix.data(), kStalePrefix.size()) == 0) {
+        continue;
+      }
+    }
+    PCHECK(stat_res == 0);
     if (S_ISDIR(s.st_mode)) {
       return true;
     }

testing/test_env.py

@@ -38,16 +38,6 @@ def fix_python_path(cmd):
   return out
 
 
-# TODO: crbug.com/362595425 - Remove once Cog supports sandboxing. This is a
-# workaround to handle a crash caused by sandbox when running
-# content_browsertests in Cider.
-def is_sandboxed_on_cog(cmd):
-  """Checks the environment is cog."""
-  return cmd.endswith('content_browsertests') and os.getcwd().startswith(
-      '/google/cog/cloud')
-
-
-
 def get_sanitizer_env(asan, lsan, msan, tsan, cfi_diag):
   """Returns the environment flags needed for sanitizer tools."""
 
@@ -389,7 +379,7 @@ def run_executable(cmd, env, stdoutfile=None, cwd=None):
   if asan or lsan or msan or tsan or cfi_diag:
     extra_env.update(get_sanitizer_env(asan, lsan, msan, tsan, cfi_diag))
 
-  if lsan or tsan or is_sandboxed_on_cog(cmd[0]):
+  if lsan or tsan:
     # LSan and TSan are not sandbox-friendly.
     cmd.append('--no-sandbox')