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Commit a1de70aa authored by Aleksa Sarai's avatar Aleksa Sarai Committed by Greg Kroah-Hartman
Browse files

cgroup: pids: use atomic64_t for pids->limit 



commit a713af394cf382a30dd28a1015cbe572f1b9ca75 upstream.

Because pids->limit can be changed concurrently (but we don't want to
take a lock because it would be needlessly expensive), use atomic64_ts
instead.

Fixes: commit 49b786ea ("cgroup: implement the PIDs subsystem")
Cc: stable@vger.kernel.org # v4.3+
Signed-off-by: default avatarAleksa Sarai <cyphar@cyphar.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 317c80c6

kernel/cgroup/pids.c

+6 −5
Original line number Diff line number Diff line
@@ -48,7 +48,7 @@ struct pids_cgroup { 
	 * %PIDS_MAX = (%PID_MAX_LIMIT + 1).

	 */

	atomic64_t			counter;

	int64_t				limit;

	atomic64_t			limit;



	/* Handle for "pids.events" */

	struct cgroup_file		events_file;
@@ -76,8 +76,8 @@ pids_css_alloc(struct cgroup_subsys_state *parent) 
	if (!pids)

		return ERR_PTR(-ENOMEM);



	pids->limit = PIDS_MAX;

	atomic64_set(&pids->counter, 0);

	atomic64_set(&pids->limit, PIDS_MAX);

	atomic64_set(&pids->events_limit, 0);

	return &pids->css;

}
@@ -149,13 +149,14 @@ static int pids_try_charge(struct pids_cgroup *pids, int num) 


	for (p = pids; parent_pids(p); p = parent_pids(p)) {

		int64_t new = atomic64_add_return(num, &p->counter);

		int64_t limit = atomic64_read(&p->limit);



		/*

		 * Since new is capped to the maximum number of pid_t, if

		 * p->limit is %PIDS_MAX then we know that this test will never

		 * fail.

		 */

		if (new > p->limit)

		if (new > limit)

			goto revert;

	}
@@ -280,7 +281,7 @@ static ssize_t pids_max_write(struct kernfs_open_file *of, char *buf, 
	 * Limit updates don't need to be mutex'd, since it isn't

	 * critical that any racing fork()s follow the new limit.

	 */

	pids->limit = limit;

	atomic64_set(&pids->limit, limit);

	return nbytes;

}
@@ -288,7 +289,7 @@ static int pids_max_show(struct seq_file *sf, void *v) 
{

	struct cgroup_subsys_state *css = seq_css(sf);

	struct pids_cgroup *pids = css_pids(css);

	int64_t limit = pids->limit;

	int64_t limit = atomic64_read(&pids->limit);



	if (limit >= PIDS_MAX)

		seq_printf(sf, "%s\n", PIDS_MAX_STR);