1// Copyright (c) 2012 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5// The following is the C version of code from base/process_utils_linux.cc. 6// We shouldn't link against C++ code in a setuid binary. 7 8// Needed for O_DIRECTORY, must be defined before fcntl.h is included 9// (and it can be included earlier than the explicit #include below 10// in some versions of glibc). 11#define _GNU_SOURCE 12 13#include "sandbox/linux/suid/process_util.h" 14 15#include <fcntl.h> 16#include <inttypes.h> 17#include <limits.h> 18#include <stdio.h> 19#include <stdlib.h> 20#include <string.h> 21#include <sys/stat.h> 22#include <sys/types.h> 23#include <unistd.h> 24 25// Ranges for the current (oom_score_adj) and previous (oom_adj) 26// flavors of OOM score. 27static const int kMaxOomScore = 1000; 28static const int kMaxOldOomScore = 15; 29 30// NOTE: This is not the only version of this function in the source: 31// the base library (in process_util_linux.cc) also has its own C++ version. 32bool AdjustOOMScore(pid_t process, int score) { 33 if (score < 0 || score > kMaxOomScore) 34 return false; 35 36 char oom_adj[27]; // "/proc/" + log_10(2**64) + "\0" 37 // 6 + 20 + 1 = 27 38 snprintf(oom_adj, sizeof(oom_adj), "/proc/%" PRIdMAX, (intmax_t)process); 39 40 const int dirfd = open(oom_adj, O_RDONLY | O_DIRECTORY); 41 if (dirfd < 0) 42 return false; 43 44 struct stat statbuf; 45 if (fstat(dirfd, &statbuf) < 0) { 46 close(dirfd); 47 return false; 48 } 49 if (getuid() != statbuf.st_uid) { 50 close(dirfd); 51 return false; 52 } 53 54 int fd = openat(dirfd, "oom_score_adj", O_WRONLY); 55 if (fd < 0) { 56 // We failed to open oom_score_adj, so let's try for the older 57 // oom_adj file instead. 58 fd = openat(dirfd, "oom_adj", O_WRONLY); 59 if (fd < 0) { 60 // Nope, that doesn't work either. 61 return false; 62 } else { 63 // If we're using the old oom_adj file, the allowed range is now 64 // [0, kMaxOldOomScore], so we scale the score. This may result in some 65 // aliasing of values, of course. 66 score = score * kMaxOldOomScore / kMaxOomScore; 67 } 68 } 69 close(dirfd); 70 71 char buf[11]; // 0 <= |score| <= kMaxOomScore; using log_10(2**32) + 1 size 72 snprintf(buf, sizeof(buf), "%d", score); 73 size_t len = strlen(buf); 74 75 ssize_t bytes_written = write(fd, buf, len); 76 close(fd); 77 return (bytes_written == (ssize_t)len); 78} 79