Message-ID: <6892ffe6.050a0220.7f033.0039.GAE@google.com>
Date: Wed, 06 Aug 2025 00:10:30 -0700
From: syzbot <syzbot+240906f6485cdb6035a7@...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?] kernel BUG in bch2_journal_pin_set (2)

Hello,

syzbot found the following issue on:

HEAD commit:    a6923c06a3b2 Merge tag 'bpf-fixes' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=128df2a2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bbdefbf39cb79f7e
dashboard link: https://syzkaller.appspot.com/bug?extid=240906f6485cdb6035a7
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-a6923c06.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6c2b6f269429/vmlinux-a6923c06.xz
kernel image: https://storage.googleapis.com/syzbot-assets/32390e35232b/bzImage-a6923c06.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+240906f6485cdb6035a7@...kaller.appspotmail.com

bcachefs (loop0): backpointer doesn't match extent it points to:
  u64s 9 type backpointer 0:8921088:0 len 0 ver 0: bucket=0:34:8 btree=extents level=0 data_type=user suboffset=0 len=8 gen=0 pos=536870913:24:U32_MAX
  u64s 7 type extent 536870913:24:U32_MAX len 24 ver 0: durability: 1 crc: c_size 8 size 24 offset 0 nonce 0 csum none 0:0  compress lz4 ptr: 0:34:8 gen 0
  u64s 9 type backpointer 0:8921088:0 len 0 ver 0: bucket=0:34:8 btree=extents level=0 data_type=user suboffset=0 len=8 gen=0 pos=536870913:24:U32_MAX, fixing
------------[ cut here ]------------
kernel BUG at fs/bcachefs/journal_reclaim.c:483!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5362 Comm: bch-copygc/loop Not tainted 6.16.0-syzkaller-11105-ga6923c06a3b2 #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:bch2_journal_pin_set+0x5c1/0x5e0 fs/bcachefs/journal_reclaim.c:483
Code: 25 3d d8 fd e9 0c ff ff ff 44 89 e9 80 e1 07 38 c1 0f 8c 88 fb ff ff 4c 89 ef e8 fa 3d d8 fd e9 7b fb ff ff e8 e0 6b 73 fd 90 <0f> 0b e8 d8 6b 73 fd 90 0f 0b e8 d0 6b 73 fd 90 0f 0b 66 66 66 66
RSP: 0018:ffffc9000d4ae728 EFLAGS: 00010293
RAX: ffffffff844c42c0 RBX: 000000000000000c RCX: ffff88801fb60000
RDX: 0000000000000000 RSI: 000000000000000c RDI: 000000000000000b
RBP: ffff888052e846b8 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52001a95cd4 R12: ffff888052ecaa38
R13: ffff888052eca898 R14: ffff888052ec9800 R15: 000000000000000b
FS:  0000000000000000(0000) GS:ffff88808d21f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff022fdc9c CR3: 0000000011ba9000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 bch2_journal_pin_add fs/bcachefs/journal_reclaim.h:48 [inline]
 bch2_journal_keys_to_write_buffer_start+0x3bb/0x3c0 fs/bcachefs/btree_write_buffer.c:793
 bch2_journal_keys_to_write_buffer fs/bcachefs/btree_write_buffer.c:510 [inline]
 fetch_wb_keys_from_journal fs/bcachefs/btree_write_buffer.c:534 [inline]
 btree_write_buffer_flush_seq+0x222/0x1a40 fs/bcachefs/btree_write_buffer.c:563
 bch2_btree_write_buffer_flush_sync+0x143/0x2c0 fs/bcachefs/btree_write_buffer.c:598
 bch2_btree_write_buffer_maybe_flush+0x7e0/0x1400 fs/bcachefs/btree_write_buffer.c:673
 bch2_backpointers_maybe_flush fs/bcachefs/backpointers.c:200 [inline]
 backpointer_target_not_found+0x110/0xc10 fs/bcachefs/backpointers.c:220
 __bch2_backpointer_get_key+0x33a/0x490 fs/bcachefs/backpointers.c:352
 bch2_backpointer_get_key+0x3e/0x60 fs/bcachefs/backpointers.c:379
 __bch2_move_data_phys+0xf82/0x1c50 fs/bcachefs/move.c:942
 bch2_evacuate_bucket+0x228/0x3a0 fs/bcachefs/move.c:1082
 bch2_copygc+0x3be3/0x4510 fs/bcachefs/movinggc.c:234
 bch2_copygc_thread+0x97a/0xe00 fs/bcachefs/movinggc.c:409
 kthread+0x711/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x3f9/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:bch2_journal_pin_set+0x5c1/0x5e0 fs/bcachefs/journal_reclaim.c:483
Code: 25 3d d8 fd e9 0c ff ff ff 44 89 e9 80 e1 07 38 c1 0f 8c 88 fb ff ff 4c 89 ef e8 fa 3d d8 fd e9 7b fb ff ff e8 e0 6b 73 fd 90 <0f> 0b e8 d8 6b 73 fd 90 0f 0b e8 d0 6b 73 fd 90 0f 0b 66 66 66 66
RSP: 0018:ffffc9000d4ae728 EFLAGS: 00010293
RAX: ffffffff844c42c0 RBX: 000000000000000c RCX: ffff88801fb60000
RDX: 0000000000000000 RSI: 000000000000000c RDI: 000000000000000b
RBP: ffff888052e846b8 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52001a95cd4 R12: ffff888052ecaa38
R13: ffff888052eca898 R14: ffff888052ec9800 R15: 000000000000000b
FS:  0000000000000000(0000) GS:ffff88808d21f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff022fdc9c CR3: 0000000011ba9000 CR4: 0000000000352ef0


---
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