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// Copyright (c) 2012 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.
// Needed for O_DIRECTORY, must be defined before fcntl.h is included
// (and it can be included earlier than the explicit #include below
// in some versions of glibc).
#define _GNU_SOURCE
#include "sandbox/linux/suid/process_util.h"
#include <fcntl.h>
#include <inttypes.h>
#include <limits.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
// Ranges for the current (oom_score_adj) and previous (oom_adj)
// flavors of OOM score.
static const int kMaxOomScore = 1000;
static const int kMaxOldOomScore = 15;
// NOTE: This is not the only version of this function in the source:
// the base library (in process_util_linux.cc) also has its own C++ version.
bool AdjustOOMScore(pid_t process, int score) {
if (score < 0 || score > kMaxOomScore)
return false;
char oom_adj[27]; // "/proc/" + log_10(2**64) + "\0"
// 6 + 20 + 1 = 27
snprintf(oom_adj, sizeof(oom_adj), "/proc/%" PRIdMAX, (intmax_t)process);
const int dirfd = open(oom_adj, O_RDONLY | O_DIRECTORY);
if (dirfd < 0)
return false;
struct stat statbuf;
if (fstat(dirfd, &statbuf) < 0) {
close(dirfd);
return false;
}
if (getuid() != statbuf.st_uid) {
close(dirfd);
return false;
}
int fd = openat(dirfd, "oom_score_adj", O_WRONLY);
if (fd < 0) {
// We failed to open oom_score_adj, so let's try for the older
// oom_adj file instead.
fd = openat(dirfd, "oom_adj", O_WRONLY);
if (fd < 0) {
// Nope, that doesn't work either.
close(dirfd);
return false;
} else {
// If we're using the old oom_adj file, the allowed range is now
// [0, kMaxOldOomScore], so we scale the score. This may result in some
// aliasing of values, of course.
score = score * kMaxOldOomScore / kMaxOomScore;
}
}
close(dirfd);
char buf[11]; // 0 <= |score| <= kMaxOomScore; using log_10(2**32) + 1 size
snprintf(buf, sizeof(buf), "%d", score);
size_t len = strlen(buf);
ssize_t bytes_written = write(fd, buf, len);
close(fd);
return (bytes_written == (ssize_t)len);
}
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