OpenE2K
/
linux
6
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

blk-throttle: fix null pointer dereference while throttling writeback IOs 

A null pointer dereference can occur when blkcg is removed manually
with writeback IOs inflight. This is caused by the following case:

Writeback kworker submit the bio and set bio->bi_cg_private to tg
in blk_throtl_assoc_bio.
Then we remove the block cgroup manually, the blkg and tg would be
freed if there is no request inflight.
When the submitted bio come back, blk_throtl_bio_endio() fetch the tg
which was already freed.

Fix this by increasing the refcount of blkg in funcion
blk_throtl_assoc_bio() so that the blkg will not be freed until the
bio_endio called.

Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jiufei Xue <jiufei.xjf@alibaba-inc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jiufei Xue 2017-10-10 11:13:32 +08:00 committed by Jens Axboe
parent 58a9edce0a
commit 53cfdc10a9
1 changed files with 10 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
block/blk-throttle.c
View File

@ -2112,8 +2112,12 @@ static inline void throtl_update_latency_buckets(struct throtl_data *td)
static void blk_throtl_assoc_bio(struct throtl_grp *tg, struct bio *bio)
{
#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
if (bio->bi_css)
if (bio->bi_css) {
if (bio->bi_cg_private)
blkg_put(tg_to_blkg(bio->bi_cg_private));
bio->bi_cg_private = tg;
blkg_get(tg_to_blkg(tg));
}
blk_stat_set_issue(&bio->bi_issue_stat, bio_sectors(bio));
#endif
}
@ -2283,8 +2287,10 @@ void blk_throtl_bio_endio(struct bio *bio)
start_time = blk_stat_time(&bio->bi_issue_stat) >> 10;
finish_time = __blk_stat_time(finish_time_ns) >> 10;
if (!start_time || finish_time <= start_time)
if (!start_time || finish_time <= start_time) {
blkg_put(tg_to_blkg(tg));
return;
}
lat = finish_time - start_time;
/* this is only for bio based driver */
@ -2314,6 +2320,8 @@ void blk_throtl_bio_endio(struct bio *bio)
tg->bio_cnt /= 2;
tg->bad_bio_cnt /= 2;
}
blkg_put(tg_to_blkg(tg));
}
#endif