diff options
| author | Jens Axboe <axboe@kernel.dk> | 2018-06-02 14:04:07 -0600 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-07-22 15:16:06 +0200 |
| commit | cc4cc98785daf355e9b6405bb5adee52d121b1b3 (patch) | |
| tree | dbe526250bbaa2b4976ea8ca52a81f97b819f8f2 /block | |
| parent | 84e0e8168c66ab9ddbd559583b60f390781d462d (diff) | |
block: don't use blocking queue entered for recursive bio submits
commit cd4a4ae4683dc2e09380118e205e057896dcda2b upstream.
If we end up splitting a bio and the queue goes away between
the initial submission and the later split submission, then we
can block forever in blk_queue_enter() waiting for the reference
to drop to zero. This will never happen, since we already hold
a reference.
Mark a split bio as already having entered the queue, so we can
just use the live non-blocking queue enter variant.
Thanks to Tetsuo Handa for the analysis.
Reported-by: syzbot+c4f9cebf9d651f6e54de@syzkaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-core.c | 4 | ||||
| -rw-r--r-- | block/blk-merge.c | 10 |
2 files changed, 13 insertions, 1 deletions
diff --git a/block/blk-core.c b/block/blk-core.c index b559b9d4f1a2..47ab2d9d02d9 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -2392,7 +2392,9 @@ blk_qc_t generic_make_request(struct bio *bio) if (bio->bi_opf & REQ_NOWAIT) flags = BLK_MQ_REQ_NOWAIT; - if (blk_queue_enter(q, flags) < 0) { + if (bio_flagged(bio, BIO_QUEUE_ENTERED)) + blk_queue_enter_live(q); + else if (blk_queue_enter(q, flags) < 0) { if (!blk_queue_dying(q) && (bio->bi_opf & REQ_NOWAIT)) bio_wouldblock_error(bio); else diff --git a/block/blk-merge.c b/block/blk-merge.c index 782940c65d8a..481dc02668f9 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -210,6 +210,16 @@ void blk_queue_split(struct request_queue *q, struct bio **bio) /* there isn't chance to merge the splitted bio */ split->bi_opf |= REQ_NOMERGE; + /* + * Since we're recursing into make_request here, ensure + * that we mark this bio as already having entered the queue. + * If not, and the queue is going away, we can get stuck + * forever on waiting for the queue reference to drop. But + * that will never happen, as we're already holding a + * reference to it. + */ + bio_set_flag(*bio, BIO_QUEUE_ENTERED); + bio_chain(split, *bio); trace_block_split(q, split, (*bio)->bi_iter.bi_sector); generic_make_request(*bio); |