Re: [syzbot] [bcachefs?] general protection fault in bch2_alloc_read

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in bch2_replicas_entry_validate

bcachefs (loop0): starting version 1.7: mi_btree_bitmap opts=metadata_checksum=none,data_checksum=none,compression=lz4,usrquota,nojournal_transaction_names
============================================
WARNING: possible recursive locking detected
6.12.0-rc2-syzkaller-g8cf0b93919e1 #0 Not tainted
--------------------------------------------
syz.0.15/5549 is trying to acquire lock:
ffff888054c00908 (&c->sb_lock){+.+.}-{3:3}, at: bch2_replicas_entry_validate+0x2a/0x80 fs/bcachefs/replicas.c:101

but task is already holding lock:
ffff888054c00908 (&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.0.15/5549:
 #0: ffff888054c00278 (&c->state_lock){+.+.}-{3:3}, at: bch2_fs_start+0x45/0x5b0 fs/bcachefs/super.c:1007
 #1: ffff888054c00908 (&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: 5549 Comm: syz.0.15 Not tainted 6.12.0-rc2-syzkaller-g8cf0b93919e1 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
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:2080
 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: 0033:0x7fd37f97f69a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd3806ffe68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fd3806ffef0 RCX: 00007fd37f97f69a
RDX: 00000000200058c0 RSI: 0000000020005900 RDI: 00007fd3806ffeb0
RBP: 00000000200058c0 R08: 00007fd3806ffef0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000020005900
R13: 00007fd3806ffeb0 R14: 00000000000058cd R15: 0000000020000000
 </TASK>


Tested on:

commit:         8cf0b939 Linux 6.12-rc2
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=12d72707980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=74c522fa0761706b
dashboard link: https://syzkaller.appspot.com/bug?extid=a1b59c8e1a3f022fd301
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.