[moderation] [bcachefs?] BUG: unable to handle kernel paging request in bch2_btree_cache_scan

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c13320499ba0 Merge tag '6.10-rc-smb3-fixes-part2' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=126dc972980000
kernel config: https://syzkaller.appspot.com/x/.config?x=e70c03a304f3c3ef
dashboard link: https://syzkaller.appspot.com/bug?extid=e9f97b25380b2cba519f
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: i386
CC: [bfo...@redhat.com kent.ov...@linux.dev linux-b...@vger.kernel.org linux-...@vger.kernel.org]

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-c1332049.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4d89011b261c/vmlinux-c1332049.xz
kernel image: https://storage.googleapis.com/syzbot-assets/86f1a107597e/bzImage-c1332049.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e9f97b...@syzkaller.appspotmail.com

BUG: unable to handle page fault for address: ffffe8ffad17f5c8
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 1543f067 P4D 1543f067 PUD 19afe067 PMD 19aff067 PTE 0
Oops: Oops: 0002 [#1] PREEMPT SMP KASAN NOPTI
CPU: 1 PID: 111 Comm: kswapd0 Not tainted 6.9.0-syzkaller-12398-gc13320499ba0 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:bch2_btree_cache_scan+0x492/0x1150 fs/bcachefs/btree_cache.c:463
Code: 48 89 fa 48 c1 ea 03 0d ff ff fb ff 21 43 2c 48 b8 00 00 00 00 00 fc ff df 80 3c 02 00 0f 85 9c 0b 00 00 49 8b 86 f8 b6 04 00 <65> 48 ff 40 38 48 b8 00 00 00 00 00 fc ff df 48 8b 54 24 50 48 c1
RSP: 0018:ffffc90000e176b0 EFLAGS: 00010246
RAX: 0000607f8107f590 RBX: ffff88801b368000 RCX: 0000000000000000
RDX: 1ffff1100cf896df RSI: ffffffff83e65ed7 RDI: ffff888067c4b6f8
RBP: ffff888067c01a48 R08: 0000000000000001 R09: fffff520001c2ebf
R10: ffffc90000e175ff R11: 0000000000000000 R12: ffff888067c01c70
R13: ffff888067c01a48 R14: ffff888067c00000 R15: 0000000000000007
FS: 0000000000000000(0000) GS:ffff88802c100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffe8ffad17f5c8 CR3: 0000000025eae000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
do_shrink_slab+0x44f/0x11c0 mm/shrinker.c:435
shrink_slab+0x18a/0x1310 mm/shrinker.c:662
shrink_one+0x493/0x7c0 mm/vmscan.c:4790
shrink_many mm/vmscan.c:4851 [inline]
lru_gen_shrink_node+0x89f/0x1750 mm/vmscan.c:4951
shrink_node mm/vmscan.c:5910 [inline]
kswapd_shrink_node mm/vmscan.c:6720 [inline]
balance_pgdat+0x1105/0x1970 mm/vmscan.c:6911
kswapd+0x5ea/0xbf0 mm/vmscan.c:7180
kthread+0x2c1/0x3a0 kernel/kthread.c:389
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>
Modules linked in:
CR2: ffffe8ffad17f5c8
---[ end trace 0000000000000000 ]---
RIP: 0010:bch2_btree_cache_scan+0x492/0x1150 fs/bcachefs/btree_cache.c:463
Code: 48 89 fa 48 c1 ea 03 0d ff ff fb ff 21 43 2c 48 b8 00 00 00 00 00 fc ff df 80 3c 02 00 0f 85 9c 0b 00 00 49 8b 86 f8 b6 04 00 <65> 48 ff 40 38 48 b8 00 00 00 00 00 fc ff df 48 8b 54 24 50 48 c1
RSP: 0018:ffffc90000e176b0 EFLAGS: 00010246
RAX: 0000607f8107f590 RBX: ffff88801b368000 RCX: 0000000000000000
RDX: 1ffff1100cf896df RSI: ffffffff83e65ed7 RDI: ffff888067c4b6f8
RBP: ffff888067c01a48 R08: 0000000000000001 R09: fffff520001c2ebf
R10: ffffc90000e175ff R11: 0000000000000000 R12: ffff888067c01c70
R13: ffff888067c01a48 R14: ffff888067c00000 R15: 0000000000000007
FS: 0000000000000000(0000) GS:ffff88802c100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffe8ffad17f5c8 CR3: 0000000025eae000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 48 89 fa mov %rdi,%rdx
3: 48 c1 ea 03 shr $0x3,%rdx
7: 0d ff ff fb ff or $0xfffbffff,%eax
c: 21 43 2c and %eax,0x2c(%rbx)
f: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
16: fc ff df
19: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
1d: 0f 85 9c 0b 00 00 jne 0xbbf
23: 49 8b 86 f8 b6 04 00 mov 0x4b6f8(%r14),%rax
* 2a: 65 48 ff 40 38 incq %gs:0x38(%rax) <-- trapping instruction
2f: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
36: fc ff df
39: 48 8b 54 24 50 mov 0x50(%rsp),%rdx
3e: 48 rex.W
3f: c1 .byte 0xc1


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