[syzbot] [bcachefs?] BUG: unable to handle kernel paging request in bch2_btree_cache_scan (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    a9cda7c0ffed Merge tag 'irq_urgent_for_v6.12_rc7' of git:/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1687135f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=64aa0d9945bd5c1
dashboard link: https://syzkaller.appspot.com/bug?extid=7b48a45a8154d8d0a75d
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-a9cda7c0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/29b6746965e0/vmlinux-a9cda7c0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/455959afbe37/bzImage-a9cda7c0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7b48a45a8154d8d0a75d@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: unable to handle page fault for address: ffffe8fffe20d038
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 1ac3f067 P4D 1ac3f067 PUD 1e8e9067 PMD 56cec067 PTE 0
Oops: Oops: 0002 [#1] PREEMPT SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 79 Comm: kswapd0 Not tainted 6.12.0-rc6-syzkaller-00318-ga9cda7c0ffed #0
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_btree_cache_scan+0xb57/0xed0 fs/bcachefs/btree_cache.c:561
Code: 24 38 0f 85 12 02 00 00 44 21 2a 48 81 c3 38 b6 04 00 48 89 d8 48 c1 e8 03 80 3c 28 00 74 08 48 89 df e8 1c 9b ea fd 48 8b 03 <65> 48 ff 40 38 41 80 3c 2e 00 74 08 4c 89 ff e8 05 9b ea fd 49 8b
RSP: 0018:ffffc900010573b8 EFLAGS: 00010246
RAX: 0000607fde60d000 RBX: ffff8880570cb638 RCX: ffffffff8bcff45d
RDX: ffff88801f06002c RSI: 0000000000000008 RDI: ffffc90001057340
RBP: dffffc0000000000 R08: ffffc90001057347 R09: 1ffff9200020ae68
R10: dffffc0000000000 R11: fffff5200020ae69 R12: 0000000000000003
R13: 00000000fffbffff R14: 1ffff9200020aed1 R15: ffffc90001057688
FS:  0000000000000000(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffe8fffe20d038 CR3: 000000000e734000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 do_shrink_slab+0x701/0x1160 mm/shrinker.c:437
 shrink_slab+0x1093/0x14d0 mm/shrinker.c:664
 shrink_one+0x43b/0x850 mm/vmscan.c:4824
 shrink_many mm/vmscan.c:4885 [inline]
 lru_gen_shrink_node mm/vmscan.c:4963 [inline]
 shrink_node+0x3791/0x3e20 mm/vmscan.c:5943
 kswapd_shrink_node mm/vmscan.c:6771 [inline]
 balance_pgdat mm/vmscan.c:6963 [inline]
 kswapd+0x1ca9/0x3700 mm/vmscan.c:7232
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/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: ffffe8fffe20d038
---[ end trace 0000000000000000 ]---
RIP: 0010:bch2_btree_cache_scan+0xb57/0xed0 fs/bcachefs/btree_cache.c:561
Code: 24 38 0f 85 12 02 00 00 44 21 2a 48 81 c3 38 b6 04 00 48 89 d8 48 c1 e8 03 80 3c 28 00 74 08 48 89 df e8 1c 9b ea fd 48 8b 03 <65> 48 ff 40 38 41 80 3c 2e 00 74 08 4c 89 ff e8 05 9b ea fd 49 8b
RSP: 0018:ffffc900010573b8 EFLAGS: 00010246
RAX: 0000607fde60d000 RBX: ffff8880570cb638 RCX: ffffffff8bcff45d
RDX: ffff88801f06002c RSI: 0000000000000008 RDI: ffffc90001057340
RBP: dffffc0000000000 R08: ffffc90001057347 R09: 1ffff9200020ae68
R10: dffffc0000000000 R11: fffff5200020ae69 R12: 0000000000000003
R13: 00000000fffbffff R14: 1ffff9200020aed1 R15: ffffc90001057688
FS:  0000000000000000(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffe8fffe20d038 CR3: 000000000e734000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	24 38                	and    $0x38,%al
   2:	0f 85 12 02 00 00    	jne    0x21a
   8:	44 21 2a             	and    %r13d,(%rdx)
   b:	48 81 c3 38 b6 04 00 	add    $0x4b638,%rbx
  12:	48 89 d8             	mov    %rbx,%rax
  15:	48 c1 e8 03          	shr    $0x3,%rax
  19:	80 3c 28 00          	cmpb   $0x0,(%rax,%rbp,1)
  1d:	74 08                	je     0x27
  1f:	48 89 df             	mov    %rbx,%rdi
  22:	e8 1c 9b ea fd       	call   0xfdea9b43
  27:	48 8b 03             	mov    (%rbx),%rax
* 2a:	65 48 ff 40 38       	incq   %gs:0x38(%rax) <-- trapping instruction
  2f:	41 80 3c 2e 00       	cmpb   $0x0,(%r14,%rbp,1)
  34:	74 08                	je     0x3e
  36:	4c 89 ff             	mov    %r15,%rdi
  39:	e8 05 9b ea fd       	call   0xfdea9b43
  3e:	49                   	rex.WB
  3f:	8b                   	.byte 0x8b


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