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| author | Jiufei Xue <jiufei.xjf@alibaba-inc.com> | 2017-10-10 11:13:32 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2017-10-10 13:09:34 -0600 |
| commit | 53cfdc10a95d03fbc82970d682a32696d19ef886 (patch) | |
| tree | 1cd5d88450b9e3f6b741f3552348555b64376804 /block/blk-throttle.c | |
| parent | 58a9edce0aa912640abe47d3fc039e6230ef848b (diff) | |
| download | lwn-53cfdc10a95d03fbc82970d682a32696d19ef886.tar.gz lwn-53cfdc10a95d03fbc82970d682a32696d19ef886.zip | |
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.c | 12 |
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 |