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 49b786ea146f ("cgroup: implement the PIDs subsystem")
Cc: stable@vger.kernel.org # v4.3+
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/kernel/cgroup_pids.c b/kernel/cgroup_pids.c
index a57242e..b8b898e 100644
--- a/kernel/cgroup_pids.c
+++ b/kernel/cgroup_pids.c
@@ -48,7 +48,7 @@
* %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 @@
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 @@
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 @@
* 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 @@
{
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);