The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 310726c33ad76cebdee312dbfafc12c1b44bf977 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '16780875786811@kroah.com' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

310726c33ad7 ("block: be a bit more careful in checking for NULL bdev while polling") 69fe0f298920 ("block: add ->poll_bio to block_device_operations") 7f36b7d02a28 ("block: move blk_crypto_bio_prep() out of blk-mq.c") a650628bde77 ("block: move submit_bio_checks() into submit_bio_noacct") 9d497e2941c3 ("block: don't protect submit_bio_checks by q_usage_counter") a08ed9aae8a3 ("block: fix double bio queue when merging in cached request path") 5f480b1a6325 ("blk-mq: use bio->bi_opf after bio is checked") 5b13bc8a3fd5 ("blk-mq: cleanup request allocation") 0c5bcc92d94a ("blk-mq: simplify the plug handling in blk_mq_submit_bio") 95febeb61bf8 ("block: fix missing queue put in error path") b637108a4022 ("blk-mq: fix filesystem I/O request allocation") b131f2011115 ("blk-mq: rename blk_attempt_bio_merge") 10c47870155b ("block: ensure cached plug request matches the current queue") 900e08075202 ("block: move queue enter logic into blk_mq_submit_bio()") c98cb5bbdab1 ("block: make bio_queue_enter() fast-path available inline") 71539717c105 ("block: split request allocation components into helpers") a1cb65377e70 ("blk-mq: only try to run plug merge if request has same queue with incoming bio") e94f68527a35 ("block: kill extra rcu lock/unlock in queue enter") 179ae84f7ef5 ("block: clean up blk_mq_submit_bio() merging") 1497a51a3287 ("block: don't bloat enter_queue with percpu_ref")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 310726c33ad76cebdee312dbfafc12c1b44bf977 Mon Sep 17 00:00:00 2001 From: Jens Axboe axboe@kernel.dk Date: Fri, 24 Feb 2023 10:01:19 -0700 Subject: [PATCH] block: be a bit more careful in checking for NULL bdev while polling

Wei reports a crash with an application using polled IO:

PGD 14265e067 P4D 14265e067 PUD 47ec50067 PMD 0 Oops: 0000 [#1] SMP CPU: 0 PID: 21915 Comm: iocore_0 Kdump: loaded Tainted: G S 5.12.0-0_fbk12_clang_7346_g1bb6f2e7058f #1 Hardware name: Wiwynn Delta Lake MP T8/Delta Lake-Class2, BIOS Y3DLM08 04/10/2022 RIP: 0010:bio_poll+0x25/0x200 Code: 0f 1f 44 00 00 0f 1f 44 00 00 55 41 57 41 56 41 55 41 54 53 48 83 ec 28 65 48 8b 04 25 28 00 00 00 48 89 44 24 20 48 8b 47 08 <48> 8b 80 70 02 00 00 4c 8b 70 50 8b 6f 34 31 db 83 fd ff 75 25 65 RSP: 0018:ffffc90005fafdf8 EFLAGS: 00010292 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 74b43cd65dd66600 RDX: 0000000000000003 RSI: ffffc90005fafe78 RDI: ffff8884b614e140 RBP: ffff88849964df78 R08: 0000000000000000 R09: 0000000000000008 R10: 0000000000000000 R11: 0000000000000000 R12: ffff88849964df00 R13: ffffc90005fafe78 R14: ffff888137d3c378 R15: 0000000000000001 FS: 00007fd195000640(0000) GS:ffff88903f400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000270 CR3: 0000000466121001 CR4: 00000000007706f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: iocb_bio_iopoll+0x1d/0x30 io_do_iopoll+0xac/0x250 __se_sys_io_uring_enter+0x3c5/0x5a0 ? __x64_sys_write+0x89/0xd0 do_syscall_64+0x2d/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x94f225d Code: 24 cc 00 00 00 41 8b 84 24 d0 00 00 00 c1 e0 04 83 e0 10 41 09 c2 8b 33 8b 53 04 4c 8b 43 18 4c 63 4b 0c b8 aa 01 00 00 0f 05 <85> c0 0f 88 85 00 00 00 29 03 45 84 f6 0f 84 88 00 00 00 41 f6 c7 RSP: 002b:00007fd194ffcd88 EFLAGS: 00000202 ORIG_RAX: 00000000000001aa RAX: ffffffffffffffda RBX: 00007fd194ffcdc0 RCX: 00000000094f225d RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000007 RBP: 00007fd194ffcdb0 R08: 0000000000000000 R09: 0000000000000008 R10: 0000000000000001 R11: 0000000000000202 R12: 00007fd269d68030 R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000000

which is due to bio->bi_bdev being NULL. This can happen if we have two tasks doing polled IO, and task B ends up completing IO from task A if they are sharing a poll queue. If task B completes the IO and puts the bio into our cache, then it can allocate that bio again before task A is done polling for it. As that would necessitate a preempt between the two tasks, it's enough to just be a bit more careful in checking for whether or not bio->bi_bdev is NULL.

Reported-and-tested-by: Wei Zhang wzhang@meta.com Cc: stable@vger.kernel.org Fixes: be4d234d7aeb ("bio: add allocation cache abstraction") Reviewed-by: Keith Busch kbusch@kernel.org Signed-off-by: Jens Axboe axboe@kernel.dk

diff --git a/block/blk-core.c b/block/blk-core.c index 5fb6856745b4..5d7e2ca75234 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -854,10 +854,16 @@ EXPORT_SYMBOL(submit_bio); */ int bio_poll(struct bio *bio, struct io_comp_batch *iob, unsigned int flags) { - struct request_queue *q = bdev_get_queue(bio->bi_bdev); blk_qc_t cookie = READ_ONCE(bio->bi_cookie); + struct block_device *bdev; + struct request_queue *q; int ret = 0;

+ bdev = READ_ONCE(bio->bi_bdev); + if (!bdev) + return 0; + + q = bdev_get_queue(bdev); if (cookie == BLK_QC_T_NONE || !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) return 0; @@ -926,7 +932,7 @@ int iocb_bio_iopoll(struct kiocb *kiocb, struct io_comp_batch *iob, */ rcu_read_lock(); bio = READ_ONCE(kiocb->private); - if (bio && bio->bi_bdev) + if (bio) ret = bio_poll(bio, iob, flags); rcu_read_unlock();