From: Ming Lei <tom.leiming@gmail.com>
Date: Thu, 1 May 2014 07:12:36 +0000 (+0800)
Subject: block: null_blk: fix use after free
X-Git-Tag: firefly_0821_release~176^2~3465^2~50^2~23
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=fc27691f3537a0df087214322467b642d1f6dedb;p=firefly-linux-kernel-4.4.55.git

block: null_blk: fix use after free

entry(cmd->ll_list) may belong to new request once end_cmd()
returns, so fix the bug with the patch.

Without the change, it is easy to observe oops when
doing null_blk(timer) test.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
---

diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index 8e7e3a0b0d24..e932398588aa 100644
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -203,8 +203,8 @@ static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer)
 		entry = llist_reverse_order(entry);
 		do {
 			cmd = container_of(entry, struct nullb_cmd, ll_list);
-			end_cmd(cmd);
 			entry = entry->next;
+			end_cmd(cmd);
 		} while (entry);
 	}