[syzbot] [bcachefs?] kernel panic: bch_dev->ref underflow, last put: bch2_trigger_alloc

syzbot
2024-05-13T10:35:36Z

Hello,

syzbot found the following issue on:

HEAD commit: 75fa778d74b7 Add linux-next specific files for 20240510
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=169304e0980000
kernel config: https://syzkaller.appspot.com/x/.config?x=ccdd3ebd6715749a
dashboard link: https://syzkaller.appspot.com/bug?extid=5c7f715a7107a608a544
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=144834d0980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11c06d24980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ad9391835bcf/disk-75fa778d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d827b3da9a26/vmlinux-75fa778d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8f32f0182388/bzImage-75fa778d.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/c5a442f16c7f/mount_0.gz

The issue was bisected to:

commit 552aa5486579c18b4f8e7ca03ef88fa573c517b5
Author: Kent Overstreet <kent.overstreet@linux.dev>
Date: Fri May 3 22:07:40 2024 +0000

bcachefs: Debug asserts for ca->ref

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14a9007c980000
final oops: https://syzkaller.appspot.com/x/report.txt?x=16a9007c980000
console output: https://syzkaller.appspot.com/x/log.txt?x=12a9007c980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5c7f715a7107a608a544@syzkaller.appspotmail.com
Fixes: 552aa5486579 ("bcachefs: Debug asserts for ca->ref")

bcachefs (loop0): mounting version 1.7: mi_btree_bitmap opts=metadata_checksum=none,data_checksum=none,nojournal_transaction_names
bcachefs (loop0): recovering from clean shutdown, journal seq 8
bcachefs (loop0): alloc_read... done
bcachefs (loop0): stripes_read... done
bcachefs (loop0): snapshots_read... done
bucket 0:4 gen 0 different types of data in same bucket: btree, sb
while marking sb, shutting down
bcachefs (loop0): inconsistency detected - emergency read only at journal seq 8
bcachefs (loop0): bch2_trans_mark_dev_sb(): error EIO
Kernel panic - not syncing: bch_dev->ref underflow, last put: __bch2_dev_put fs/bcachefs/sb-members.h:110 [inline]
Kernel panic - not syncing: bch_dev->ref underflow, last put: bch2_dev_put fs/bcachefs/sb-members.h:121 [inline]
Kernel panic - not syncing: bch_dev->ref underflow, last put: bch2_trigger_alloc+0x2934/0x3b90 fs/bcachefs/alloc_background.c:913
CPU: 1 PID: 5093 Comm: syz-executor498 Not tainted 6.9.0-rc7-next-20240510-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
panic+0x349/0x860 kernel/panic.c:347
__bch2_dev_put fs/bcachefs/sb-members.h:109 [inline]
bch2_dev_put fs/bcachefs/sb-members.h:121 [inline]
bch2_trans_mark_dev_sbs_flags+0xaa7/0xab0 fs/bcachefs/buckets.c:1467
bch2_run_recovery_pass+0xf0/0x1e0 fs/bcachefs/recovery_passes.c:182
bch2_run_recovery_passes+0x19e/0x820 fs/bcachefs/recovery_passes.c:225
bch2_fs_recovery+0x2370/0x3700 fs/bcachefs/recovery.c:804
bch2_fs_start+0x356/0x5b0 fs/bcachefs/super.c:1031
bch2_fs_open+0xa8d/0xdf0 fs/bcachefs/super.c:2123
bch2_mount+0x71d/0x1320 fs/bcachefs/fs.c:1917
legacy_get_tree+0xee/0x190 fs/fs_context.c:662
vfs_get_tree+0x90/0x2a0 fs/super.c:1780
do_new_mount+0x2be/0xb40 fs/namespace.c:3352
do_mount fs/namespace.c:3692 [inline]
__do_sys_mount fs/namespace.c:3898 [inline]
__se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3875
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7facf885c8fa
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 5e 04 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe54cb8d38 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffe54cb8d50 RCX: 00007facf885c8fa
RDX: 0000000020005b00 RSI: 0000000020005b40 RDI: 00007ffe54cb8d50
RBP: 0000000000000004 R08: 00007ffe54cb8d90 R09: 0000000000005b4c
R10: 0000000000000000 R11: 0000000000000282 R12: 0000000000000000
R13: 00007ffe54cb8d90 R14: 0000000000000003 R15: 0000000001000000
</TASK>
Kernel Offset: disabled
Rebooting in 86400 seconds..

---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup