Message-ID: <66fed783.050a0220.9ec68.0051.GAE@google.com>
Date: Thu, 03 Oct 2024 10:42:27 -0700
From: syzbot <syzbot+4d24267b490e2b68a5fa@...kaller.appspotmail.com>
To: kent.overstreet@...ux.dev, linux-bcachefs@...r.kernel.org, 
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [bcachefs?] possible deadlock in bch2_replicas_entry_validate

Hello,

syzbot found the following issue on:

HEAD commit:    e32cde8d2bd7 Merge tag 'sched_ext-for-6.12-rc1-fixes-1' of..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=105b939f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1f009dd80b3799c2
dashboard link: https://syzkaller.appspot.com/bug?extid=4d24267b490e2b68a5fa
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=1366e927980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=111c7dd0580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/08f3ba449e03/disk-e32cde8d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/17bcace1ab90/vmlinux-e32cde8d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/da9183ac0145/bzImage-e32cde8d.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/4c7b8b3c4819/mount_0.gz

The issue was bisected to:

commit 49fd90b2cc332b8607a616d99d4bb792f18208b9
Author: Kent Overstreet <kent.overstreet@...ux.dev>
Date:   Wed Sep 25 22:17:31 2024 +0000

    bcachefs: Fix unlocked access to c->disk_sb.sb in bch2_replicas_entry_validate()

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=14b8a3d0580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=16b8a3d0580000
console output: https://syzkaller.appspot.com/x/log.txt?x=12b8a3d0580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4d24267b490e2b68a5fa@...kaller.appspotmail.com
Fixes: 49fd90b2cc33 ("bcachefs: Fix unlocked access to c->disk_sb.sb in bch2_replicas_entry_validate()")

WARNING: The mand mount option has been deprecated and
         and is ignored by this kernel. Remove the mand
         option from the mount to silence this warning.
=======================================================
bcachefs (loop0): starting version 1.7: mi_btree_bitmap opts=errors=continue,compression=zstd,norecovery,recovery_pass_last=check_dirents,nojournal_transaction_names,version_upgrade=none
============================================
WARNING: possible recursive locking detected
6.12.0-rc1-syzkaller-00031-ge32cde8d2bd7 #0 Not tainted
--------------------------------------------
syz-executor340/5221 is trying to acquire lock:
ffff888078a80908 (&c->sb_lock){+.+.}-{3:3}, at: bch2_replicas_entry_validate+0x2a/0x80 fs/bcachefs/replicas.c:101

but task is already holding lock:
ffff888078a80908 (&c->sb_lock){+.+.}-{3:3}, at: bch2_read_superblock_clean+0x36/0x520 fs/bcachefs/sb-clean.c:149

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&c->sb_lock);
  lock(&c->sb_lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by syz-executor340/5221:
 #0: ffff888078a80278 (&c->state_lock){+.+.}-{3:3}, at: bch2_fs_start+0x45/0x5b0 fs/bcachefs/super.c:1007
 #1: ffff888078a80908 (&c->sb_lock){+.+.}-{3:3}, at: bch2_read_superblock_clean+0x36/0x520 fs/bcachefs/sb-clean.c:149

stack backtrace:
CPU: 0 UID: 0 PID: 5221 Comm: syz-executor340 Not tainted 6.12.0-rc1-syzkaller-00031-ge32cde8d2bd7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_deadlock_bug+0x483/0x620 kernel/locking/lockdep.c:3037
 check_deadlock kernel/locking/lockdep.c:3089 [inline]
 validate_chain+0x15e2/0x5920 kernel/locking/lockdep.c:3891
 __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5202
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
 bch2_replicas_entry_validate+0x2a/0x80 fs/bcachefs/replicas.c:101
 journal_entry_data_usage_validate+0x2b6/0x690 fs/bcachefs/journal_io.c:608
 bch2_sb_clean_validate_late fs/bcachefs/sb-clean.c:40 [inline]
 bch2_read_superblock_clean+0x207/0x520 fs/bcachefs/sb-clean.c:168
 bch2_fs_recovery+0x1f4/0x39c0 fs/bcachefs/recovery.c:639
 bch2_fs_start+0x356/0x5b0 fs/bcachefs/super.c:1037
 bch2_fs_get_tree+0xd68/0x1710 fs/bcachefs/fs.c:2071
 vfs_get_tree+0x90/0x2b0 fs/super.c:1800
 do_new_mount+0x2be/0xb40 fs/namespace.c:3507
 do_mount fs/namespace.c:3847 [inline]
 __do_sys_mount fs/namespace.c:4055 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4032
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2478bb0c3a
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:00007ffecc9ae478 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffecc9ae490 RCX: 00007f2478bb0c3a
RDX: 0000000020005d80 RSI: 0000000020000240 RDI: 00007ffecc9ae490
RBP: 0000000000000004 R08: 00007ffecc9ae4d0 R09: 0000000000005daf
R10: 0000000000000044 R11: 0000000000000282 R12: 0000000000000044
R13: 00007ffecc9ae4d0 R14: 0000000000000003 R15: 0000000001000000
 </TASK>


---
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