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Commit 799105d5 authored by Greg Thelen's avatar Greg Thelen Committed by Tejun Heo
Browse files

cgroups: fix cgroup_event_listener error handling 



The error handling in cgroup_event_listener.c did not correctly deal
with either an error opening either <control_file> or
cgroup.event_control.  Due to an uninitialized variable the program
exit code was undefined if either of these opens failed.

This patch simplifies and corrects cgroup_event_listener.c error
handling by:
1. using err*() rather than printf(),exit()
2. depending on process exit to close open files

With this patch failures always return non-zero error.

Signed-off-by: default avatarGreg Thelen <gthelen@google.com>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 92e015b1

tools/cgroup/cgroup_event_listener.c

+22 −50
Original line number Diff line number Diff line
@@ -5,6 +5,7 @@ 
 */



#include <assert.h>

#include <err.h>

#include <errno.h>

#include <fcntl.h>

#include <libgen.h>
@@ -15,7 +16,7 @@ 


#include <sys/eventfd.h>



#define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>\n"

#define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>"



int main(int argc, char **argv)

{
@@ -26,49 +27,33 @@ int main(int argc, char **argv) 
	char line[LINE_MAX];

	int ret;



	if (argc != 3) {

		fputs(USAGE_STR, stderr);

		return 1;

	}

	if (argc != 3)

		errx(1, "%s", USAGE_STR);



	cfd = open(argv[1], O_RDONLY);

	if (cfd == -1) {

		fprintf(stderr, "Cannot open %s: %s\n", argv[1],

				strerror(errno));

		goto out;

	}

	if (cfd == -1)

		err(1, "Cannot open %s", argv[1]);



	ret = snprintf(event_control_path, PATH_MAX, "%s/cgroup.event_control",

			dirname(argv[1]));

	if (ret >= PATH_MAX) {

		fputs("Path to cgroup.event_control is too long\n", stderr);

		goto out;

	}

	if (ret >= PATH_MAX)

		errx(1, "Path to cgroup.event_control is too long");



	event_control = open(event_control_path, O_WRONLY);

	if (event_control == -1) {

		fprintf(stderr, "Cannot open %s: %s\n", event_control_path,

				strerror(errno));

		goto out;

	}

	if (event_control == -1)

		err(1, "Cannot open %s", event_control_path);



	efd = eventfd(0, 0);

	if (efd == -1) {

		perror("eventfd() failed");

		goto out;

	}

	if (efd == -1)

		err(1, "eventfd() failed");



	ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]);

	if (ret >= LINE_MAX) {

		fputs("Arguments string is too long\n", stderr);

		goto out;

	}

	if (ret >= LINE_MAX)

		errx(1, "Arguments string is too long");



	ret = write(event_control, line, strlen(line) + 1);

	if (ret == -1) {

		perror("Cannot write to cgroup.event_control");

		goto out;

	}

	if (ret == -1)

		err(1, "Cannot write to cgroup.event_control");



	while (1) {

		uint64_t result;
@@ -77,34 +62,21 @@ int main(int argc, char **argv) 
		if (ret == -1) {

			if (errno == EINTR)

				continue;

			perror("Cannot read from eventfd");

			break;

			err(1, "Cannot read from eventfd");

		}

		assert(ret == sizeof(result));



		ret = access(event_control_path, W_OK);

		if ((ret == -1) && (errno == ENOENT)) {

			puts("The cgroup seems to have removed.");

				ret = 0;

			break;

		}



		if (ret == -1) {

			perror("cgroup.event_control "

					"is not accessible any more");

			break;

		}

		if (ret == -1)

			err(1, "cgroup.event_control is not accessible any more");



		printf("%s %s: crossed\n", argv[1], argv[2]);

	}



out:

	if (efd >= 0)

		close(efd);

	if (event_control >= 0)

		close(event_control);

	if (cfd >= 0)

		close(cfd);



	return (ret != 0);

	return 0;

}