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

sandbox/linux/suid/sandbox.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.
 
 // http://code.google.com/p/chromium/wiki/LinuxSUIDSandbox
 
 #define _GNU_SOURCE
 #include <asm/unistd.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
 #include <sched.h>
 #include <signal.h>
 #include <stdarg.h>
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/prctl.h>
 #include <sys/resource.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/time.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 #include "linux_util.h"
+#include "process_util.h"
 #include "suid_unsafe_environment_variables.h"
 
 #if !defined(CLONE_NEWPID)
 #define CLONE_NEWPID 0x20000000
 #endif
 
 static const char kSandboxDescriptorEnvironmentVarName[] = "SBX_D";
 
 // These are the magic byte values which the sandboxed process uses to request
 // that it be chrooted.
@@ skipping 263 matching lines @@
   // a dummy socket, which has a unique inode number. Then it asks the sandbox
   // host to find the PID of the process holding that fd by searching /proc.
   //
   // Since the zygote and renderers are all spawned by this setuid executable,
   // their entries in /proc are owned by root and only readable by root. In
   // order to search /proc for the fd we want, this setuid executable has to
   // double as a helper and perform the search. The code block below does this
   // when you call it with --find-inode INODE_NUMBER.
   if (argc == 3 && (0 == strcmp(argv[1], kFindInodeSwitch))) {
     pid_t pid;
-    char *endptr;
+    char* endptr;
     ino_t inode = strtoull(argv[2], &endptr, 10);
     if (inode == ULLONG_MAX || *endptr)
       return 1;
     if (!FindProcessHoldingSocket(&pid, inode))
       return 1;
     printf("%d\n", pid);
     return 0;
   }
+  // Likewise, we cannot adjust /proc/pid/oom_adj for sandboxed renderers
+  // because those files are owned by root. So we need another helper here.
+  if (argc == 4 && (0 == strcmp(argv[1], kAdjustOOMScoreSwitch))) {
+    char* endptr;
+    int score;
+    pid_t pid = strtoul(argv[2], &endptr, 10);
+    if (pid == ULONG_MAX || *endptr)
+      return 1;
+    score = strtol(argv[3], &endptr, 10);
+    if (score == LONG_MAX || score == LONG_MIN || *endptr)
+      return 1;
+    return AdjustOOMScore(pid, score);
+  }
 
   if (!MoveToNewPIDNamespace())
     return 1;
   if (!SpawnChrootHelper())
     return 1;
   if (!DropRoot())
     return 1;
   if (!SetupChildEnvironment())
     return 1;
 
   execv(argv[1], &argv[1]);
   FatalError("execv failed");
 
   return 1;
 }