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authorJiufei Xue <jiufei.xjf@alibaba-inc.com>2017-10-10 06:13:32 +0300
committerJens Axboe <axboe@kernel.dk>2017-10-10 22:09:34 +0300
commit53cfdc10a95d03fbc82970d682a32696d19ef886 (patch)
tree1cd5d88450b9e3f6b741f3552348555b64376804 /block/blk-throttle.c
parent58a9edce0aa912640abe47d3fc039e6230ef848b (diff)
downloadlinux-53cfdc10a95d03fbc82970d682a32696d19ef886.tar.xz
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>
Diffstat (limited to 'block/blk-throttle.c')
-rw-r--r--block/blk-throttle.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 0fea76aa0f3f..fe49c465ec86 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -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