Linux: Adjust /proc/pid/oom_adj to sacrifice plugin and renderer processes to...

sandbox/linux/suid/process_util_linux.c

+// Copyright (c) 2009 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.
+
+// The following is the C version of code from base/process_utils_linux.cc.
+// We shouldn't link against C++ code in a setuid binary.
+
+#include "process_util.h"
+
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+bool AdjustOOMScore(pid_t process, int score) {
+  if (score < 0 || score > 15)
+    return false;
+
+  char oom_adj[PATH_MAX];

[agl, 2009/12/09 21:19:14]

Rather than use PATH_MAX here, it would be clearer if we had 6 /* "/proc/" */ +
20 /* log_2(2**64) */ + 9 /* "/oom_adj\0" */

+  snprintf(oom_adj, sizeof(oom_adj), "/proc/%lu", process);
+
+  struct stat statbuf;
+  if (stat(oom_adj, &statbuf) < 0)
+    return false;
+  if (getuid() != statbuf.st_uid)

[agl, 2009/12/09 21:19:14]

If one was being really careful one would open the directory, check the UID and
use openat to get the oom_adj. However, it's actually not worth it in this case.

+    return false;
+
+  strcat(oom_adj, "/oom_adj");
+  int fd = open(oom_adj, O_WRONLY);
+  if (fd < 0)
+    return false;
+
+  char buf[3];
+  snprintf(buf, sizeof(buf), "%d", score);
+  size_t len = strlen(buf);
+
+  ssize_t bytes_written = write(fd, buf, len);
+  close(fd);
+  return (bytes_written == len);
+}