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/*
* Copyright © 2014 Canonical Ltd.
*
* This program is free software: you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 3, as published
* by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranties of
* MERCHANTABILITY, SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR
* PURPOSE. See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Authors:
* Ted Gould <ted.gould@canonical.com>
*/
#define _POSIX_C_SOURCE 200809L
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
int
main (int argc, char * argv[])
{
if (argc != 3) {
fprintf(stderr, "Usage: %s <pid> <value>\n", argv[0]);
exit(EXIT_FAILURE);
}
/* Not we turn the pid into an integer and back so that we can ensure we don't
get used for nefarious tasks. */
int pidval = atoi(argv[1]);
if ((pidval < 1) || (pidval >= 32768)) {
fprintf(stderr, "PID passed is invalid: %d\n", pidval);
exit(EXIT_FAILURE);
}
/* Not we turn the oom value into an integer and back so that we can ensure we don't
get used for nefarious tasks. */
int oomval = atoi(argv[2]);
if ((oomval < -1000) || (oomval >= 1000)) {
fprintf(stderr, "OOM Value passed is invalid: %d\n", oomval);
exit(EXIT_FAILURE);
}
/* Open up the PID directory first, to ensure that it is actually one of
ours, so that we can't be used to set a OOM value on just anything */
char pidpath[32];
snprintf(pidpath, sizeof(pidpath), "/proc/%d", pidval);
int piddir = open(pidpath, O_RDONLY | O_DIRECTORY);
if (piddir < 0) {
fprintf(stderr, "Unable open PID directory '%s' for '%d': %s\n", pidpath, pidval, strerror(errno));
exit(EXIT_FAILURE);
}
struct stat piddirstat = {0};
if (fstat(piddir, &piddirstat) < 0) {
close(piddir);
fprintf(stderr, "Unable stat PID directory '%s' for '%d': %s\n", pidpath, pidval, strerror(errno));
exit(EXIT_FAILURE);
}
if (getuid() != piddirstat.st_uid) {
close(piddir);
fprintf(stderr, "PID directory '%s' is not owned by %d but by %d\n", pidpath, getuid(), piddirstat.st_uid);
exit(EXIT_FAILURE);
}
/* Looks good, let's try to get the actual oom_adj_score file to write
the value to it. */
int adj = openat(piddir, "oom_score_adj", O_WRONLY);
int openerr = errno;
if (adj < 0) {
close(piddir);
/* ENOENT happens a fair amount because of races, so it's not
worth printing a warning about */
if (openerr != ENOENT) {
fprintf(stderr, "Unable to set OOM value of '%d' on '%d': %s\n", oomval, pidval, strerror(openerr));
exit(EXIT_FAILURE);
} else {
exit(EXIT_SUCCESS);
}
}
char oomstring[32];
snprintf(oomstring, sizeof(oomstring), "%d", oomval);
size_t writesize = write(adj, oomstring, strlen(oomstring));
int writeerr = errno;
close(adj);
close(piddir);
if (writesize == strlen(oomstring))
exit(EXIT_SUCCESS);
if (writeerr != 0)
fprintf(stderr, "Unable to set OOM value of '%d' on '%d': %s\n", oomval, pidval, strerror(writeerr));
else
/* No error, but yet, wrong size. Not sure, what could cause this. */
fprintf(stderr, "Unable to set OOM value of '%d' on '%d': Wrote %d bytes\n", oomval, pidval, (int)writesize);
exit(EXIT_FAILURE);
}
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