* [PATCH 0/2] Fix a race condition triggered by submit_bio() @ 2019-07-30 18:17 Bart Van Assche 2019-07-30 18:17 ` [PATCH 1/2] block: Verify whether blk_queue_enter() is used when necessary Bart Van Assche 2019-07-30 18:17 ` [PATCH 2/2] block: Fix a race condition in submit_bio() Bart Van Assche 0 siblings, 2 replies; 8+ messages in thread From: Bart Van Assche @ 2019-07-30 18:17 UTC (permalink / raw) To: Jens Axboe; +Cc: linux-block, Christoph Hellwig, Bart Van Assche Hi Jens, One of the consequences of the switch to blk-mq is that generic_make_request() calls, a function called by submit_bio(), must be protected by a blk_queue_enter() / blk_queue_exit() pair to avoid that the block-cgroup functions called by generic_make_request() trigger a race condition. This patch series makes the kernel report a warning if that race condition is hit and also adds the necessary protection in submit_bio(). Please consider these patches for kernel v5.4. Thanks, Bart. Bart Van Assche (2): block: Verify whether blk_queue_enter() is used when necessary block: Fix a race condition in submit_bio() block/blk-cgroup.c | 2 ++ block/blk-core.c | 34 +++++++++++++++++++++++++++++++++- include/linux/blk-cgroup.h | 2 ++ include/linux/blkdev.h | 8 ++++++++ 4 files changed, 45 insertions(+), 1 deletion(-) -- 2.22.0.709.g102302147b-goog ^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH 1/2] block: Verify whether blk_queue_enter() is used when necessary 2019-07-30 18:17 [PATCH 0/2] Fix a race condition triggered by submit_bio() Bart Van Assche @ 2019-07-30 18:17 ` Bart Van Assche 2019-07-31 1:46 ` Ming Lei 2019-07-30 18:17 ` [PATCH 2/2] block: Fix a race condition in submit_bio() Bart Van Assche 1 sibling, 1 reply; 8+ messages in thread From: Bart Van Assche @ 2019-07-30 18:17 UTC (permalink / raw) To: Jens Axboe Cc: linux-block, Christoph Hellwig, Bart Van Assche, Tejun Heo, Ming Lei, Hannes Reinecke, Johannes Thumshirn, Alexandru Moise, Joseph Qi It is required to protect blkg_lookup() calls with a blk_queue_enter() / blk_queue_exit() pair. Since it is nontrivial to verify whether this is the case, verify this at runtime. Only perform this verification if CONFIG_LOCKDEP=y to avoid that unnecessary runtime overhead is added. Note: using lock_acquire()/lock_release() to verify whether blkg_lookup() is protected correctly is not possible since lock_acquire() and lock_release() must be called from the same task and since blk_queue_enter() and blk_queue_exit() can be called from different tasks. Suggested-by: Tejun Heo <tj@kernel.org> Cc: Tejun Heo <tj@kernel.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Ming Lei <ming.lei@redhat.com> Cc: Hannes Reinecke <hare@suse.com> Cc: Johannes Thumshirn <jthumshirn@suse.de> Cc: Alexandru Moise <00moses.alexander00@gmail.com> Cc: Joseph Qi <joseph.qi@linux.alibaba.com> Signed-off-by: Bart Van Assche <bvanassche@acm.org> --- block/blk-cgroup.c | 2 ++ block/blk-core.c | 21 +++++++++++++++++++++ include/linux/blk-cgroup.h | 2 ++ include/linux/blkdev.h | 8 ++++++++ 4 files changed, 33 insertions(+) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 24ed26957367..04b6e962eefb 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -196,6 +196,8 @@ struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg, { struct blkcg_gq *blkg; + WARN_ON_ONCE(!blk_entered_queue(q)); + /* * Hint didn't match. Look up from the radix tree. Note that the * hint can only be updated under queue_lock as otherwise @blkg diff --git a/block/blk-core.c b/block/blk-core.c index 5878504a29af..ff27c3080348 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -389,6 +389,25 @@ struct request_queue *blk_alloc_queue(gfp_t gfp_mask) } EXPORT_SYMBOL(blk_alloc_queue); +#ifdef CONFIG_PROVE_LOCKING +/** + * blk_entered_queue() - whether or not it is safe to access cgroup information + * @q: request queue pointer + * + * In order to avoid races between accessing cgroup information and the cgroup + * information removal from inside __blk_release_queue(), any code that accesses + * cgroup information must be protected by a blk_queue_enter()/blk_queue_exit() + * pair or must be called after queue cleanup progressed to a stage in which + * only the cleanup code accesses the queue. + */ +bool blk_entered_queue(struct request_queue *q) +{ + return percpu_ref_is_dying(&q->q_usage_counter) || + !percpu_ref_is_zero(&q->q_usage_counter); +} +EXPORT_SYMBOL(blk_entered_queue); +#endif + /** * blk_queue_enter() - try to increase q->q_usage_counter * @q: request queue pointer @@ -878,6 +897,8 @@ generic_make_request_checks(struct bio *bio) goto end_io; } + WARN_ON_ONCE(!blk_entered_queue(q)); + /* * For a REQ_NOWAIT based request, return -EOPNOTSUPP * if queue is not a request based queue. diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h index 689a58231288..397df0719bda 100644 --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -358,6 +358,8 @@ static inline struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg, { struct blkcg_gq *blkg; + WARN_ON_ONCE(!blk_entered_queue(q)); + if (blkcg == &blkcg_root) return q->root_blkg; diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 96a29a72fd4a..e57651888450 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -856,6 +856,14 @@ extern int sg_scsi_ioctl(struct request_queue *, struct gendisk *, fmode_t, extern int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags); extern void blk_queue_exit(struct request_queue *q); +#ifdef CONFIG_PROVE_LOCKING +extern bool blk_entered_queue(struct request_queue *q); +#else +static inline bool blk_entered_queue(struct request_queue *q) +{ + return true; +} +#endif extern void blk_sync_queue(struct request_queue *q); extern int blk_rq_map_user(struct request_queue *, struct request *, struct rq_map_data *, void __user *, unsigned long, -- 2.22.0.709.g102302147b-goog ^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH 1/2] block: Verify whether blk_queue_enter() is used when necessary 2019-07-30 18:17 ` [PATCH 1/2] block: Verify whether blk_queue_enter() is used when necessary Bart Van Assche @ 2019-07-31 1:46 ` Ming Lei 2019-07-31 18:26 ` Bart Van Assche 0 siblings, 1 reply; 8+ messages in thread From: Ming Lei @ 2019-07-31 1:46 UTC (permalink / raw) To: Bart Van Assche Cc: Jens Axboe, linux-block, Christoph Hellwig, Tejun Heo, Hannes Reinecke, Johannes Thumshirn, Alexandru Moise, Joseph Qi On Tue, Jul 30, 2019 at 11:17:56AM -0700, Bart Van Assche wrote: > It is required to protect blkg_lookup() calls with a blk_queue_enter() / > blk_queue_exit() pair. Since it is nontrivial to verify whether this is Could you explain the reason why the blk_queue_enter()/blk_queue_exit() pair is required for blkg_lookup()? And comment on blkg_lookup() only mentioned RCU read lock is needed. The request queue reference counter is supposed to be held for any caller of submit_bio(), why isn't that ref count enough? Thanks, Ming ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH 1/2] block: Verify whether blk_queue_enter() is used when necessary 2019-07-31 1:46 ` Ming Lei @ 2019-07-31 18:26 ` Bart Van Assche 0 siblings, 0 replies; 8+ messages in thread From: Bart Van Assche @ 2019-07-31 18:26 UTC (permalink / raw) To: Ming Lei Cc: Jens Axboe, linux-block, Christoph Hellwig, Tejun Heo, Hannes Reinecke, Johannes Thumshirn, Alexandru Moise, Joseph Qi On 7/30/19 6:46 PM, Ming Lei wrote: > On Tue, Jul 30, 2019 at 11:17:56AM -0700, Bart Van Assche wrote: >> It is required to protect blkg_lookup() calls with a blk_queue_enter() / >> blk_queue_exit() pair. Since it is nontrivial to verify whether this is > > Could you explain the reason why the blk_queue_enter()/blk_queue_exit() > pair is required for blkg_lookup()? And comment on blkg_lookup() only > mentioned RCU read lock is needed. > > The request queue reference counter is supposed to be held for any > caller of submit_bio(), why isn't that ref count enough? This patch was added to my own tree before commit 47cdee29ef9d ("block: move blk_exit_queue into __blk_release_queue") went upstream. Since blk_exit_queue() has been moved from blk_cleanup_queue() into __blk_release_queue() I don' think that we need this patch series. I will drop these two patches. Bart. ^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH 2/2] block: Fix a race condition in submit_bio() 2019-07-30 18:17 [PATCH 0/2] Fix a race condition triggered by submit_bio() Bart Van Assche 2019-07-30 18:17 ` [PATCH 1/2] block: Verify whether blk_queue_enter() is used when necessary Bart Van Assche @ 2019-07-30 18:17 ` Bart Van Assche 2019-07-30 18:18 ` syzbot 2019-07-31 1:53 ` Ming Lei 1 sibling, 2 replies; 8+ messages in thread From: Bart Van Assche @ 2019-07-30 18:17 UTC (permalink / raw) To: Jens Axboe Cc: linux-block, Christoph Hellwig, Bart Van Assche, Tejun Heo, Ming Lei, Hannes Reinecke, Johannes Thumshirn, Alexandru Moise, Joseph Qi, syzbot+ff9ab4a23afa7553 generic_make_request_checks() needs to be protected by a blk_queue_enter() / blk_queue_exit() pair because it calls blkcg_bio_issue_check() and because that last function calls blkg_lookup(). This patch fixes https://syzkaller.appspot.com/bug?id=ff9ab4a23afa7553fb79f745a92be87ba4144508. This patch also fixes the following kernel warning, triggered by blktests: WARNING: CPU: 5 PID: 10706 at block/blk-core.c:903 generic_make_request_checks+0x9c6/0xe60 RIP: 0010:generic_make_request_checks+0x9c6/0xe60 Call Trace: generic_make_request+0x7a/0x5c0 submit_bio+0x92/0x280 mpage_readpages+0x2b1/0x300 blkdev_readpages+0x1d/0x20 read_pages+0xd9/0x2c0 __do_page_cache_readahead+0x2e0/0x310 force_page_cache_readahead+0xfb/0x170 page_cache_sync_readahead+0x28d/0x2a0 generic_file_read_iter+0xc13/0x1530 blkdev_read_iter+0x7d/0x90 new_sync_read+0x2c5/0x3d0 __vfs_read+0x7b/0x90 vfs_read+0xc6/0x1f0 ksys_read+0xc3/0x160 __x64_sys_read+0x43/0x50 do_syscall_64+0x71/0x270 entry_SYSCALL_64_after_hwframe+0x49/0xbe Cc: Tejun Heo <tj@kernel.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Ming Lei <ming.lei@redhat.com> Cc: Hannes Reinecke <hare@suse.com> Cc: Johannes Thumshirn <jthumshirn@suse.de> Cc: Alexandru Moise <00moses.alexander00@gmail.com> Cc: Joseph Qi <joseph.qi@linux.alibaba.com> Reported-by: syzbot+ff9ab4a23afa7553@syzkaller.appspotmail.com Signed-off-by: Bart Van Assche <bvanassche@acm.org> --- block/blk-core.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/block/blk-core.c b/block/blk-core.c index ff27c3080348..cd844c54e9f1 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1150,6 +1150,9 @@ EXPORT_SYMBOL_GPL(direct_make_request); */ blk_qc_t submit_bio(struct bio *bio) { + struct request_queue *q = bio->bi_disk->queue; + blk_qc_t ret; + if (blkcg_punt_bio_submit(bio)) return BLK_QC_T_NONE; @@ -1182,7 +1185,15 @@ blk_qc_t submit_bio(struct bio *bio) } } - return generic_make_request(bio); + if (unlikely(blk_queue_enter(q, 0) < 0)) { + bio->bi_status = BLK_STS_IOERR; + bio->bi_end_io(bio); + return BLK_QC_T_NONE; + } + ret = generic_make_request(bio); + blk_queue_exit(q); + + return ret; } EXPORT_SYMBOL(submit_bio); -- 2.22.0.709.g102302147b-goog ^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH 2/2] block: Fix a race condition in submit_bio() 2019-07-30 18:17 ` [PATCH 2/2] block: Fix a race condition in submit_bio() Bart Van Assche @ 2019-07-30 18:18 ` syzbot 2019-07-31 1:53 ` Ming Lei 1 sibling, 0 replies; 8+ messages in thread From: syzbot @ 2019-07-30 18:18 UTC (permalink / raw) To: Bart Van Assche Cc: 00moses.alexander00, axboe, bvanassche, hare, hch, joseph.qi, jthumshirn, linux-block, ming.lei, tj > generic_make_request_checks() needs to be protected by a > blk_queue_enter() / blk_queue_exit() pair because it calls > blkcg_bio_issue_check() and because that last function calls > blkg_lookup(). > This patch fixes > https://syzkaller.appspot.com/bug?id=ff9ab4a23afa7553fb79f745a92be87ba4144508. > This patch also fixes the following kernel warning, triggered by > blktests: > WARNING: CPU: 5 PID: 10706 at block/blk-core.c:903 > generic_make_request_checks+0x9c6/0xe60 > RIP: 0010:generic_make_request_checks+0x9c6/0xe60 > Call Trace: > generic_make_request+0x7a/0x5c0 > submit_bio+0x92/0x280 > mpage_readpages+0x2b1/0x300 > blkdev_readpages+0x1d/0x20 > read_pages+0xd9/0x2c0 > __do_page_cache_readahead+0x2e0/0x310 > force_page_cache_readahead+0xfb/0x170 > page_cache_sync_readahead+0x28d/0x2a0 > generic_file_read_iter+0xc13/0x1530 > blkdev_read_iter+0x7d/0x90 > new_sync_read+0x2c5/0x3d0 > __vfs_read+0x7b/0x90 > vfs_read+0xc6/0x1f0 > ksys_read+0xc3/0x160 > __x64_sys_read+0x43/0x50 > do_syscall_64+0x71/0x270 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > Cc: Tejun Heo <tj@kernel.org> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Ming Lei <ming.lei@redhat.com> > Cc: Hannes Reinecke <hare@suse.com> > Cc: Johannes Thumshirn <jthumshirn@suse.de> > Cc: Alexandru Moise <00moses.alexander00@gmail.com> > Cc: Joseph Qi <joseph.qi@linux.alibaba.com> > Reported-by: syzbot+ff9ab4a23afa7553@syzkaller.appspotmail.com > Signed-off-by: Bart Van Assche <bvanassche@acm.org> > --- > block/blk-core.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > diff --git a/block/blk-core.c b/block/blk-core.c > index ff27c3080348..cd844c54e9f1 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -1150,6 +1150,9 @@ EXPORT_SYMBOL_GPL(direct_make_request); > */ > blk_qc_t submit_bio(struct bio *bio) > { > + struct request_queue *q = bio->bi_disk->queue; > + blk_qc_t ret; > + > if (blkcg_punt_bio_submit(bio)) > return BLK_QC_T_NONE; > @@ -1182,7 +1185,15 @@ blk_qc_t submit_bio(struct bio *bio) > } > } > - return generic_make_request(bio); > + if (unlikely(blk_queue_enter(q, 0) < 0)) { > + bio->bi_status = BLK_STS_IOERR; > + bio->bi_end_io(bio); > + return BLK_QC_T_NONE; > + } > + ret = generic_make_request(bio); > + blk_queue_exit(q); > + > + return ret; > } > EXPORT_SYMBOL(submit_bio); > -- > 2.22.0.709.g102302147b-goog I see the command but can't find the corresponding bug. The email is sent to syzbot+HASH@syzkaller.appspotmail.com address but the HASH does not correspond to any known bug. Please double check the address. ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH 2/2] block: Fix a race condition in submit_bio() 2019-07-30 18:17 ` [PATCH 2/2] block: Fix a race condition in submit_bio() Bart Van Assche 2019-07-30 18:18 ` syzbot @ 2019-07-31 1:53 ` Ming Lei 2019-07-31 1:53 ` syzbot 1 sibling, 1 reply; 8+ messages in thread From: Ming Lei @ 2019-07-31 1:53 UTC (permalink / raw) To: Bart Van Assche Cc: Jens Axboe, linux-block, Christoph Hellwig, Tejun Heo, Hannes Reinecke, Johannes Thumshirn, Alexandru Moise, Joseph Qi, syzbot+ff9ab4a23afa7553 On Tue, Jul 30, 2019 at 11:17:57AM -0700, Bart Van Assche wrote: > generic_make_request_checks() needs to be protected by a > blk_queue_enter() / blk_queue_exit() pair because it calls > blkcg_bio_issue_check() and because that last function calls > blkg_lookup(). > > This patch fixes https://syzkaller.appspot.com/bug?id=ff9ab4a23afa7553fb79f745a92be87ba4144508. > > This patch also fixes the following kernel warning, triggered by > blktests: > > WARNING: CPU: 5 PID: 10706 at block/blk-core.c:903 generic_make_request_checks+0x9c6/0xe60 > RIP: 0010:generic_make_request_checks+0x9c6/0xe60 > Call Trace: > generic_make_request+0x7a/0x5c0 > submit_bio+0x92/0x280 > mpage_readpages+0x2b1/0x300 > blkdev_readpages+0x1d/0x20 > read_pages+0xd9/0x2c0 > __do_page_cache_readahead+0x2e0/0x310 > force_page_cache_readahead+0xfb/0x170 > page_cache_sync_readahead+0x28d/0x2a0 > generic_file_read_iter+0xc13/0x1530 > blkdev_read_iter+0x7d/0x90 > new_sync_read+0x2c5/0x3d0 > __vfs_read+0x7b/0x90 > vfs_read+0xc6/0x1f0 > ksys_read+0xc3/0x160 > __x64_sys_read+0x43/0x50 > do_syscall_64+0x71/0x270 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > Cc: Tejun Heo <tj@kernel.org> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Ming Lei <ming.lei@redhat.com> > Cc: Hannes Reinecke <hare@suse.com> > Cc: Johannes Thumshirn <jthumshirn@suse.de> > Cc: Alexandru Moise <00moses.alexander00@gmail.com> > Cc: Joseph Qi <joseph.qi@linux.alibaba.com> > Reported-by: syzbot+ff9ab4a23afa7553@syzkaller.appspotmail.com > Signed-off-by: Bart Van Assche <bvanassche@acm.org> > --- > block/blk-core.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/block/blk-core.c b/block/blk-core.c > index ff27c3080348..cd844c54e9f1 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -1150,6 +1150,9 @@ EXPORT_SYMBOL_GPL(direct_make_request); > */ > blk_qc_t submit_bio(struct bio *bio) > { > + struct request_queue *q = bio->bi_disk->queue; > + blk_qc_t ret; > + > if (blkcg_punt_bio_submit(bio)) > return BLK_QC_T_NONE; > > @@ -1182,7 +1185,15 @@ blk_qc_t submit_bio(struct bio *bio) > } > } > > - return generic_make_request(bio); > + if (unlikely(blk_queue_enter(q, 0) < 0)) { > + bio->bi_status = BLK_STS_IOERR; > + bio->bi_end_io(bio); > + return BLK_QC_T_NONE; > + } > + ret = generic_make_request(bio); > + blk_queue_exit(q); No, nested blk_queue_enter() is easy to cause deadlock. Thanks, Ming ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Re: [PATCH 2/2] block: Fix a race condition in submit_bio() 2019-07-31 1:53 ` Ming Lei @ 2019-07-31 1:53 ` syzbot 0 siblings, 0 replies; 8+ messages in thread From: syzbot @ 2019-07-31 1:53 UTC (permalink / raw) To: Ming Lei Cc: 00moses.alexander00, axboe, bvanassche, hare, hch, joseph.qi, jthumshirn, linux-block, ming.lei, tj > On Tue, Jul 30, 2019 at 11:17:57AM -0700, Bart Van Assche wrote: >> generic_make_request_checks() needs to be protected by a >> blk_queue_enter() / blk_queue_exit() pair because it calls >> blkcg_bio_issue_check() and because that last function calls >> blkg_lookup(). >> This patch fixes >> https://syzkaller.appspot.com/bug?id=ff9ab4a23afa7553fb79f745a92be87ba4144508. >> This patch also fixes the following kernel warning, triggered by >> blktests: >> WARNING: CPU: 5 PID: 10706 at block/blk-core.c:903 >> generic_make_request_checks+0x9c6/0xe60 >> RIP: 0010:generic_make_request_checks+0x9c6/0xe60 >> Call Trace: >> generic_make_request+0x7a/0x5c0 >> submit_bio+0x92/0x280 >> mpage_readpages+0x2b1/0x300 >> blkdev_readpages+0x1d/0x20 >> read_pages+0xd9/0x2c0 >> __do_page_cache_readahead+0x2e0/0x310 >> force_page_cache_readahead+0xfb/0x170 >> page_cache_sync_readahead+0x28d/0x2a0 >> generic_file_read_iter+0xc13/0x1530 >> blkdev_read_iter+0x7d/0x90 >> new_sync_read+0x2c5/0x3d0 >> __vfs_read+0x7b/0x90 >> vfs_read+0xc6/0x1f0 >> ksys_read+0xc3/0x160 >> __x64_sys_read+0x43/0x50 >> do_syscall_64+0x71/0x270 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe >> Cc: Tejun Heo <tj@kernel.org> >> Cc: Christoph Hellwig <hch@lst.de> >> Cc: Ming Lei <ming.lei@redhat.com> >> Cc: Hannes Reinecke <hare@suse.com> >> Cc: Johannes Thumshirn <jthumshirn@suse.de> >> Cc: Alexandru Moise <00moses.alexander00@gmail.com> >> Cc: Joseph Qi <joseph.qi@linux.alibaba.com> >> Reported-by: syzbot+ff9ab4a23afa7553@syzkaller.appspotmail.com >> Signed-off-by: Bart Van Assche <bvanassche@acm.org> >> --- >> block/blk-core.c | 13 ++++++++++++- >> 1 file changed, 12 insertions(+), 1 deletion(-) >> diff --git a/block/blk-core.c b/block/blk-core.c >> index ff27c3080348..cd844c54e9f1 100644 >> --- a/block/blk-core.c >> +++ b/block/blk-core.c >> @@ -1150,6 +1150,9 @@ EXPORT_SYMBOL_GPL(direct_make_request); >> */ >> blk_qc_t submit_bio(struct bio *bio) >> { >> + struct request_queue *q = bio->bi_disk->queue; >> + blk_qc_t ret; >> + >> if (blkcg_punt_bio_submit(bio)) >> return BLK_QC_T_NONE; >> @@ -1182,7 +1185,15 @@ blk_qc_t submit_bio(struct bio *bio) >> } >> } >> - return generic_make_request(bio); >> + if (unlikely(blk_queue_enter(q, 0) < 0)) { >> + bio->bi_status = BLK_STS_IOERR; >> + bio->bi_end_io(bio); >> + return BLK_QC_T_NONE; >> + } >> + ret = generic_make_request(bio); >> + blk_queue_exit(q); > No, nested blk_queue_enter() is easy to cause deadlock. > Thanks, > Ming I see the command but can't find the corresponding bug. The email is sent to syzbot+HASH@syzkaller.appspotmail.com address but the HASH does not correspond to any known bug. Please double check the address. ^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2019-07-31 18:26 UTC | newest] Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2019-07-30 18:17 [PATCH 0/2] Fix a race condition triggered by submit_bio() Bart Van Assche 2019-07-30 18:17 ` [PATCH 1/2] block: Verify whether blk_queue_enter() is used when necessary Bart Van Assche 2019-07-31 1:46 ` Ming Lei 2019-07-31 18:26 ` Bart Van Assche 2019-07-30 18:17 ` [PATCH 2/2] block: Fix a race condition in submit_bio() Bart Van Assche 2019-07-30 18:18 ` syzbot 2019-07-31 1:53 ` Ming Lei 2019-07-31 1:53 ` syzbot
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