linux-kernel - [syzbot] WARNING: refcount bug in blk_mq_free

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Message-ID: <00000000000093372a05c3ad0902@google.com>
Date:   Mon, 31 May 2021 21:47:20 -0700
From:   syzbot <syzbot+836f6f41af3c5867a8b9@...kaller.appspotmail.com>
To:     axboe@...nel.dk, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: [syzbot] WARNING: refcount bug in blk_mq_free_request (3)

Hello,

syzbot found the following issue on:

HEAD commit:    d7c5303f Merge tag 'net-5.13-rc4' of git://git.kernel.org/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=125b6e37d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=aeeaaad9464418bb
dashboard link: https://syzkaller.appspot.com/bug?extid=836f6f41af3c5867a8b9

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+836f6f41af3c5867a8b9@...kaller.appspotmail.com

refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 2924 at lib/refcount.c:28 refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28
Modules linked in:
CPU: 0 PID: 2924 Comm: kworker/0:1H Not tainted 5.13.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: kblockd blk_mq_run_work_fn
RIP: 0010:refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28
Code: e9 db fe ff ff 48 89 df e8 4c 31 e9 fd e9 8a fe ff ff e8 62 a8 a4 fd 48 c7 c7 60 21 c2 89 c6 05 be 76 e5 09 01 e8 fc c0 05 05 <0f> 0b e9 af fe ff ff 0f 1f 84 00 00 00 00 00 41 56 41 55 41 54 55
RSP: 0018:ffffc90008cd78c0 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88801fb18000 RSI: ffffffff815c1805 RDI: fffff5200119af0a
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815bb63e R11: 0000000000000000 R12: ffff8880a9d70ae8
R13: ffffe8ffffc45300 R14: 0000000000000001 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000185f848 CR3: 00000000543ac000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __refcount_sub_and_test include/linux/refcount.h:283 [inline]
 __refcount_dec_and_test include/linux/refcount.h:315 [inline]
 refcount_dec_and_test include/linux/refcount.h:333 [inline]
 blk_mq_free_request+0x4d0/0x640 block/blk-mq.c:533
 __blk_mq_end_request block/blk-mq.c:558 [inline]
 blk_mq_end_request+0x41a/0x510 block/blk-mq.c:567
 blk_mq_dispatch_rq_list+0xf4d/0x1fa0 block/blk-mq.c:1398
 __blk_mq_do_dispatch_sched+0x3bc/0x910 block/blk-mq-sched.c:191
 blk_mq_do_dispatch_sched block/blk-mq-sched.c:204 [inline]
 __blk_mq_sched_dispatch_requests+0x361/0x490 block/blk-mq-sched.c:325
 blk_mq_sched_dispatch_requests+0xfb/0x180 block/blk-mq-sched.c:351
 __blk_mq_run_hw_queue+0xd8/0x150 block/blk-mq.c:1499
 blk_mq_run_work_fn+0x55/0x70 block/blk-mq.c:1831
 process_one_work+0x98d/0x1600 kernel/workqueue.c:2276
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2422
 kthread+0x3b1/0x4a0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294


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