From 21974061cfb3c4b0b1a83447fb5e7cdcd06e56dc Mon Sep 17 00:00:00 2001 From: Mike Krinkin Date: Sun, 19 Jul 2015 09:53:17 +0300 Subject: [PATCH] null_blk: fix use-after-free problem end_cmd finishes request associated with nullb_cmd struct, so we should save pointer to request_queue in a local variable before calling end_cmd. The problem was causes general protection fault with slab poisoning enabled. Fixes: 8b70f45e2eb2 ("null_blk: restart request processing on completion handler") Tested-by: Akinobu Mita Signed-off-by: Mike Krinkin Signed-off-by: Jens Axboe --- drivers/block/null_blk.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c index 69de41a87b74..3177b245d2bd 100644 --- a/drivers/block/null_blk.c +++ b/drivers/block/null_blk.c @@ -240,19 +240,19 @@ static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer) while ((entry = llist_del_all(&cq->list)) != NULL) { entry = llist_reverse_order(entry); do { + struct request_queue *q = NULL; + cmd = container_of(entry, struct nullb_cmd, ll_list); entry = entry->next; + if (cmd->rq) + q = cmd->rq->q; end_cmd(cmd); - if (cmd->rq) { - struct request_queue *q = cmd->rq->q; - - if (!q->mq_ops && blk_queue_stopped(q)) { - spin_lock(q->queue_lock); - if (blk_queue_stopped(q)) - blk_start_queue(q); - spin_unlock(q->queue_lock); - } + if (q && !q->mq_ops && blk_queue_stopped(q)) { + spin_lock(q->queue_lock); + if (blk_queue_stopped(q)) + blk_start_queue(q); + spin_unlock(q->queue_lock); } } while (entry); }