[syzbot] [bcachefs?] kernel BUG in bch2_bkey_pack_pos_lossy (2)

[syzbot <syzbot+a6af6dbf934175da5161@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    90b83efa6701 Merge tag 'bpf-next-6.16' of git://git.kernel..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=16a2c970580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ae6d9a7dd3ac8772
dashboard link: https://syzkaller.appspot.com/bug?extid=a6af6dbf934175da5161
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=159907f4580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1758a482580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fc8b15fe0000/disk-90b83efa.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/01f6377bcdf4/vmlinux-90b83efa.xz
kernel image: https://storage.googleapis.com/syzbot-assets/afd1bac4b4ac/bzImage-90b83efa.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/6c680e5364cd/mount_0.gz

The issue was bisected to:

commit cd3cdb1ef706a1ac725194d81858d58375739b25
Author: Kent Overstreet <kent.overstreet@linux.dev>
Date:   Tue Apr 22 13:14:19 2025 +0000

    bcachefs: Single err message for btree node reads

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=14841ed4580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=16841ed4580000
console output: https://syzkaller.appspot.com/x/log.txt?x=12841ed4580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a6af6dbf934175da5161@syzkaller.appspotmail.com
Fixes: cd3cdb1ef706 ("bcachefs: Single err message for btree node reads")

bcachefs (loop0): invalid bkey in btree_node btree=subvolumes level=0: u64s 8 type snapshot 0:4294967295:0 len 0 ver 0: subvol parent          0 children          0          0 subvol 1 tree 0
  invalid key type for btree subvolumes (snapshot), deleting
------------[ cut here ]------------
kernel BUG at fs/bcachefs/bkey.c:389!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 1 UID: 0 PID: 5831 Comm: read_btree_node Not tainted 6.15.0-syzkaller-07774-g90b83efa6701 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:set_inc_field_lossy fs/bcachefs/bkey.c:389 [inline]
RIP: 0010:bch2_bkey_pack_pos_lossy+0x13de/0x24e0 fs/bcachefs/bkey.c:518
Code: e8 57 ce 08 fe 48 ba 00 00 00 00 00 fc ff df e9 a5 f8 ff ff e8 c3 d5 a7 fd 90 0f 0b e8 bb d5 a7 fd 90 0f 0b e8 b3 d5 a7 fd 90 <0f> 0b e8 ab d5 a7 fd 90 0f 0b e8 a3 d5 a7 fd 90 0f 0b f3 0f 1e fa
RSP: 0018:ffffc900043aeb40 EFLAGS: 00010293
RAX: ffffffff8418244d RBX: 0000090000000000 RCX: ffff888030f41e00
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000090000000000
RBP: ffffc900043aed78 R08: ffffffffffffffff R09: ffffffffffffffff
R10: ffffffffffffffff R11: ffffffffffffffff R12: ffff88814c4490c4
R13: fffff700ffffffff R14: 0000000000000000 R15: fffffffffffffffe
FS:  0000000000000000(0000) GS:ffff888125d98000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005633c0c98470 CR3: 000000003443a000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 bkey_pack_pos fs/bcachefs/bkey.h:382 [inline]
 __build_ro_aux_tree+0xb21/0x1800 fs/bcachefs/bset.c:743
 bch2_bset_build_aux_tree+0x3f5/0x570 fs/bcachefs/bset.c:787
 bch2_btree_node_read_done+0x39e4/0x4f60 fs/bcachefs/btree_io.c:1322
 btree_node_read_work+0x426/0xe30 fs/bcachefs/btree_io.c:1400
 bch2_btree_node_read+0x887/0x29f0 fs/bcachefs/btree_io.c:-1
 bch2_btree_node_fill+0xd12/0x14f0 fs/bcachefs/btree_cache.c:994
 bch2_btree_node_get_noiter+0xa2c/0x1000 fs/bcachefs/btree_cache.c:1261
 found_btree_node_is_readable fs/bcachefs/btree_node_scan.c:85 [inline]
 try_read_btree_node fs/bcachefs/btree_node_scan.c:220 [inline]
 read_btree_nodes_worker+0x1319/0x1e20 fs/bcachefs/btree_node_scan.c:269
 kthread+0x70e/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x3fc/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:set_inc_field_lossy fs/bcachefs/bkey.c:389 [inline]
RIP: 0010:bch2_bkey_pack_pos_lossy+0x13de/0x24e0 fs/bcachefs/bkey.c:518
Code: e8 57 ce 08 fe 48 ba 00 00 00 00 00 fc ff df e9 a5 f8 ff ff e8 c3 d5 a7 fd 90 0f 0b e8 bb d5 a7 fd 90 0f 0b e8 b3 d5 a7 fd 90 <0f> 0b e8 ab d5 a7 fd 90 0f 0b e8 a3 d5 a7 fd 90 0f 0b f3 0f 1e fa
RSP: 0018:ffffc900043aeb40 EFLAGS: 00010293
RAX: ffffffff8418244d RBX: 0000090000000000 RCX: ffff888030f41e00
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000090000000000
RBP: ffffc900043aed78 R08: ffffffffffffffff R09: ffffffffffffffff
R10: ffffffffffffffff R11: ffffffffffffffff R12: ffff88814c4490c4
R13: fffff700ffffffff R14: 0000000000000000 R15: fffffffffffffffe
FS:  0000000000000000(0000) GS:ffff888125c98000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055f7477e8168 CR3: 0000000034d24000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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