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sched/rt: pick_next_rt_entity(): check list_entry

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commit 7c4a5b89a0 upstream.

Commit 326587b840 ("sched: fix goto retry in pick_next_task_rt()")
removed any path which could make pick_next_rt_entity() return NULL.
However, BUG_ON(!rt_se) in _pick_next_task_rt() (the only caller of
pick_next_rt_entity()) still checks the error condition, which can
never happen, since list_entry() never returns NULL.
Remove the BUG_ON check, and instead emit a warning in the only
possible error condition here: the queue being empty which should
never happen.

Fixes: 326587b840 ("sched: fix goto retry in pick_next_task_rt()")
Signed-off-by: Pietro Borrello <borrello@diag.uniroma1.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20230128-list-entry-null-check-sched-v3-1-b1a71bd1ac6b@diag.uniroma1.it
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Fixes CVE-2023-1077: sched/rt: pick_next_rt_entity(): check list_entry
  An insufficient list empty checking in pick_next_rt_entity().  The
  _pick_next_task_rt() checks pick_next_rt_entity() returns NULL or not
  but pick_next_rt_entity() never returns NULL.  So, even if the list is
  empty, _pick_next_task_rt() continues its process. ]
Signed-off-by: Srish Srinivasan <ssrish@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pietro Borrello 2023-02-06 22:33:54 +00:00 committed by Greg Kroah-Hartman
parent b3cd44bff8
commit 84d90fb72a
1 changed files with 4 additions and 1 deletions
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5
kernel/sched/rt.c
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@ -1522,6 +1522,8 @@ static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
BUG_ON(idx >= MAX_RT_PRIO);
queue = array->queue + idx;
if (SCHED_WARN_ON(list_empty(queue)))
return NULL;
next = list_entry(queue->next, struct sched_rt_entity, run_list);
return next;
@ -1535,7 +1537,8 @@ static struct task_struct *_pick_next_task_rt(struct rq *rq)
do {
rt_se = pick_next_rt_entity(rq, rt_rq);
BUG_ON(!rt_se);
if (unlikely(!rt_se))
return NULL;
rt_rq = group_rt_rq(rt_se);
} while (rt_rq);