Because pids->limit can be changed concurrently (but we don't want to take a lock because it would be needlessly expensive), use the appropriate memory barriers.
Fixes: commit 49b786ea146f ("cgroup: implement the PIDs subsystem") Cc: stable@vger.kernel.org # v4.3+ Signed-off-by: Aleksa Sarai cyphar@cyphar.com --- kernel/cgroup/pids.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/cgroup/pids.c b/kernel/cgroup/pids.c index 8e513a573fe9..a726e4a20177 100644 --- a/kernel/cgroup/pids.c +++ b/kernel/cgroup/pids.c @@ -152,7 +152,7 @@ static int pids_try_charge(struct pids_cgroup *pids, int num) * p->limit is %PIDS_MAX then we know that this test will never * fail. */ - if (new > p->limit) + if (new > READ_ONCE(p->limit)) goto revert; }
@@ -277,7 +277,7 @@ 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; + WRITE_ONCE(pids->limit, limit); return nbytes; }
@@ -285,7 +285,7 @@ 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 = READ_ONCE(pids->limit);
if (limit >= PIDS_MAX) seq_printf(sf, "%s\n", PIDS_MAX_STR);