syzbot


WARNING: refcount bug in blk_mq_free_request (2)

Status: fixed on 2020/06/30 18:57
Subsystems: block
[Documentation on labels]
Reported-by: syzbot+f4316dab9d4518b755eb@syzkaller.appspotmail.com
Fix commit: de6346ecbc8f nbd: protect cmd->status with cmd->lock
First crash: 1790d, last: 1749d
Cause bisection: introduced by (bisect log) :
commit 12f5b93145450c750f315657ef239a314811aeeb
Author: Keith Busch <keith.busch@intel.com>
Date: Tue May 29 13:52:28 2018 +0000

  blk-mq: Remove generation seqeunce

Crash: WARNING in blk_mq_bio_to_request (log)
Repro: C syz .config
  
Fix bisection: failed (error log, bisect log)
  
Discussions (1)
Title Replies (including bot) Last reply
WARNING: refcount bug in blk_mq_free_request (2) 2 (4) 2019/08/06 22:39
Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING: refcount bug in blk_mq_free_request (3) block 1 1088d 1084d 0/26 auto-closed as invalid on 2021/09/25 02:34
upstream WARNING: refcount bug in blk_mq_free_request block 1 1998d 1992d 0/26 auto-closed as invalid on 2019/05/29 00:00

Sample crash report:
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 16 at lib/refcount.c:190 refcount_sub_and_test_checked lib/refcount.c:190 [inline]
WARNING: CPU: 1 PID: 16 at lib/refcount.c:190 refcount_sub_and_test_checked+0x1d0/0x200 lib/refcount.c:180
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 16 Comm: ksoftirqd/1 Not tainted 5.3.0-rc3 #91
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 panic+0x2dc/0x755 kernel/panic.c:219
 __warn.cold+0x20/0x4c kernel/panic.c:576
 report_bug+0x263/0x2b0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:179 [inline]
 fixup_bug arch/x86/kernel/traps.c:174 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
 invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1026
RIP: 0010:refcount_sub_and_test_checked lib/refcount.c:190 [inline]
RIP: 0010:refcount_sub_and_test_checked+0x1d0/0x200 lib/refcount.c:180
Code: 1d 7e b3 64 06 31 ff 89 de e8 9c a3 35 fe 84 db 75 94 e8 53 a2 35 fe 48 c7 c7 80 02 c6 87 c6 05 5e b3 64 06 01 e8 18 15 07 fe <0f> 0b e9 75 ff ff ff e8 34 a2 35 fe e9 6e ff ff ff 48 89 df e8 b7
RSP: 0018:ffff8880a9917bb0 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000100 RSI: ffffffff815c3ba6 RDI: ffffed1015322f68
RBP: ffff8880a9917c48 R08: ffff8880a990a440 R09: fffffbfff134ae10
R10: fffffbfff134ae0f R11: ffffffff89a5707f R12: 00000000ffffffff
R13: 0000000000000001 R14: ffff8880a9917c20 R15: 0000000000000000
 refcount_dec_and_test_checked+0x1b/0x20 lib/refcount.c:220
 blk_mq_free_request+0x3b8/0x580 block/blk-mq.c:524
 __blk_mq_end_request block/blk-mq.c:550 [inline]
 blk_mq_end_request+0x456/0x560 block/blk-mq.c:559
 nbd_complete_rq+0x42/0x50 drivers/block/nbd.c:322
 blk_done_softirq+0x2fe/0x4d0 block/blk-softirq.c:37
 __do_softirq+0x262/0x98c kernel/softirq.c:292
 run_ksoftirqd kernel/softirq.c:603 [inline]
 run_ksoftirqd+0x8e/0x110 kernel/softirq.c:595
 smpboot_thread_fn+0x6a3/0xa40 kernel/smpboot.c:165
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Kernel Offset: disabled
Rebooting in 86400 seconds..

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2019/08/05 18:22 upstream e21a712a9685 6affd8e8 .config console log report syz C ci-upstream-kasan-gce-selinux-root
2019/08/05 17:51 upstream e21a712a9685 6affd8e8 .config console log report syz C ci-upstream-kasan-gce-root
2019/08/05 19:15 linux-next b1645c0cbd48 6affd8e8 .config console log report syz C ci-upstream-linux-next-kasan-gce-root
2019/08/05 17:14 upstream e21a712a9685 6affd8e8 .config console log report ci-upstream-kasan-gce-root
2019/06/26 03:24 linux-next 902031767aec 0a8d1a96 .config console log report ci-upstream-linux-next-kasan-gce-root
* Struck through repros no longer work on HEAD.