From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Bart Van Assche To: Jens Axboe Cc: linux-block@vger.kernel.org, Christoph Hellwig , Bart Van Assche , Ming Lei , Joseph Qi Subject: [PATCH] blk-mq: Avoid that submitting a bio concurrently with device removal triggers a crash Date: Tue, 10 Apr 2018 14:30:35 -0600 Message-Id: <20180410203035.26167-1-bart.vanassche@wdc.com> MIME-Version: 1.0 Content-Type: text/plain Return-Path: bart.vanassche@wdc.com List-ID: Because blkcg_exit_queue() is now called from inside blk_cleanup_queue() it is no longer safe to access cgroup information during or after the blk_cleanup_queue() call. Hence protect the generic_make_request_checks() call with blk_queue_enter() / blk_queue_exit(). Reported-by: Ming Lei Fixes: a063057d7c73 ("block: Fix a race between request queue removal and the block cgroup controller") Signed-off-by: Bart Van Assche Cc: Ming Lei Cc: Joseph Qi --- block/blk-core.c | 32 ++++++++++++++++++++++++++------ 1 file changed, 26 insertions(+), 6 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index 34e2f2227fd9..a330cd2829e1 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -2386,8 +2386,19 @@ blk_qc_t generic_make_request(struct bio *bio) * yet. */ struct bio_list bio_list_on_stack[2]; + blk_mq_req_flags_t flags = bio->bi_opf & REQ_NOWAIT ? + BLK_MQ_REQ_NOWAIT : 0; + struct request_queue *q = bio->bi_disk->queue; blk_qc_t ret = BLK_QC_T_NONE; + if (blk_queue_enter(q, flags) < 0) { + if (!blk_queue_dying(q) && (bio->bi_opf & REQ_NOWAIT)) + bio_wouldblock_error(bio); + else + bio_io_error(bio); + return ret; + } + if (!generic_make_request_checks(bio)) goto out; @@ -2424,11 +2435,20 @@ blk_qc_t generic_make_request(struct bio *bio) bio_list_init(&bio_list_on_stack[0]); current->bio_list = bio_list_on_stack; do { - struct request_queue *q = bio->bi_disk->queue; - blk_mq_req_flags_t flags = bio->bi_opf & REQ_NOWAIT ? - BLK_MQ_REQ_NOWAIT : 0; + bool enter_succeeded = true; - if (likely(blk_queue_enter(q, flags) == 0)) { + if (unlikely(q != bio->bi_disk->queue)) { + flags = bio->bi_opf & REQ_NOWAIT ? BLK_MQ_REQ_NOWAIT : + 0; + blk_queue_exit(q); + q = bio->bi_disk->queue; + if (blk_queue_enter(q, flags) < 0) { + enter_succeeded = false; + q = NULL; + } + } + + if (enter_succeeded) { struct bio_list lower, same; /* Create a fresh bio_list for all subordinate requests */ @@ -2436,8 +2456,6 @@ blk_qc_t generic_make_request(struct bio *bio) bio_list_init(&bio_list_on_stack[0]); ret = q->make_request_fn(q, bio); - blk_queue_exit(q); - /* sort new bios into those for a lower level * and those for the same level */ @@ -2464,6 +2482,8 @@ blk_qc_t generic_make_request(struct bio *bio) current->bio_list = NULL; /* deactivate */ out: + if (q) + blk_queue_exit(q); return ret; } EXPORT_SYMBOL(generic_make_request); -- 2.16.2