From: Aleksa Sarai cyphar@cyphar.com
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
--- kernel/cgroup/pids.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)
--- a/kernel/cgroup/pids.c +++ b/kernel/cgroup/pids.c @@ -45,7 +45,7 @@ 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; @@ -73,8 +73,8 @@ pids_css_alloc(struct cgroup_subsys_stat 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; } @@ -146,13 +146,14 @@ static int pids_try_charge(struct pids_c
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; }
@@ -277,7 +278,7 @@ set_limit: * 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; }
@@ -285,7 +286,7 @@ static int pids_max_show(struct seq_file { 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);