提交 a41b816c 编写于 作者: J Joseph Qi 提交者: Jens Axboe

blk-throttle: fix NULL pointer dereference in throtl_schedule_pending_timer

I have encountered a NULL pointer dereference in
throtl_schedule_pending_timer:
  [  413.735396] BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
  [  413.735535] IP: [<ffffffff812ebbbf>] throtl_schedule_pending_timer+0x3f/0x210
  [  413.735643] PGD 22c8cf067 PUD 22cb34067 PMD 0
  [  413.735713] Oops: 0000 [#1] SMP
  ......

This is caused by the following case:
  blk_throtl_bio
    throtl_schedule_next_dispatch  <= sq is top level one without parent
      throtl_schedule_pending_timer
        sq_to_tg(sq)->td->throtl_slice  <= sq_to_tg(sq) returns NULL

Fix it by using sq_to_td instead of sq_to_tg(sq)->td, which will always
return a valid td.

Fixes: 297e3d85 ("blk-throttle: make throtl_slice tunable")
Signed-off-by: NJoseph Qi <qijiang.qj@alibaba-inc.com>
Reviewed-by: NShaohua Li <shli@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>
上级 9bd2bbc0
......@@ -698,7 +698,7 @@ static void throtl_dequeue_tg(struct throtl_grp *tg)
static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
unsigned long expires)
{
unsigned long max_expire = jiffies + 8 * sq_to_tg(sq)->td->throtl_slice;
unsigned long max_expire = jiffies + 8 * sq_to_td(sq)->throtl_slice;
/*
* Since we are adjusting the throttle limit dynamically, the sleep
......
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