[syzbot] [netfs?] general protection fault in netfs_write_collection_worker

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    e32cde8d2bd7 Merge tag 'sched_ext-for-6.12-rc1-fixes-1' of..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=136ae580580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1b5201b91035a876
dashboard link: https://syzkaller.appspot.com/bug?extid=af5c06208fa71bf31b16
compiler:       gcc (Debian 12.2.0-14) 12.2.0, 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-e32cde8d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b8759dd370e1/vmlinux-e32cde8d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c770fb4b8507/bzImage-e32cde8d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+af5c06208fa71bf31b16@xxxxxxxxxxxxxxxxxxxxxxxxx

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 0 UID: 0 PID: 1109 Comm: kworker/u32:8 Not tainted 6.12.0-rc1-syzkaller-00031-ge32cde8d2bd7 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: events_unbound netfs_write_collection_worker
RIP: 0010:folioq_folio include/linux/folio_queue.h:277 [inline]
RIP: 0010:netfs_writeback_unlock_folios fs/netfs/write_collect.c:107 [inline]
RIP: 0010:netfs_collect_write_results fs/netfs/write_collect.c:493 [inline]
RIP: 0010:netfs_write_collection_worker+0x1c97/0x4780 fs/netfs/write_collect.c:551
Code: 4c 39 fb 0f 83 25 04 00 00 e8 e5 94 54 ff 44 8b 2c 24 41 83 fd 1e 0f 87 77 23 00 00 4a 8d 44 ed 08 48 89 44 24 30 48 c1 e8 03 <42> 80 3c 30 00 0f 85 4f 23 00 00 4a 8b 5c ed 08 48 89 df e8 d1 da
RSP: 0018:ffffc90005d6fae8 EFLAGS: 00010202
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff8238f165
RDX: ffff888026c4a440 RSI: ffffffff8238f40b RDI: 0000000000000005
RBP: 0000000000000000 R08: ffff88805f4fc600 R09: 000000000000001e
R10: 0000000000000000 R11: 0000000000000000 R12: 000000000000002c
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff88805f4fc5fa
FS:  0000000000000000(0000) GS:ffff88806a600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055960e035c38 CR3: 0000000056af8000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 process_one_work+0x9c5/0x1ba0 kernel/workqueue.c:3229
 process_scheduled_works kernel/workqueue.c:3310 [inline]
 worker_thread+0x6c8/0xf00 kernel/workqueue.c:3391
 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:
---[ end trace 0000000000000000 ]---
RIP: 0010:folioq_folio include/linux/folio_queue.h:277 [inline]
RIP: 0010:netfs_writeback_unlock_folios fs/netfs/write_collect.c:107 [inline]
RIP: 0010:netfs_collect_write_results fs/netfs/write_collect.c:493 [inline]
RIP: 0010:netfs_write_collection_worker+0x1c97/0x4780 fs/netfs/write_collect.c:551
Code: 4c 39 fb 0f 83 25 04 00 00 e8 e5 94 54 ff 44 8b 2c 24 41 83 fd 1e 0f 87 77 23 00 00 4a 8d 44 ed 08 48 89 44 24 30 48 c1 e8 03 <42> 80 3c 30 00 0f 85 4f 23 00 00 4a 8b 5c ed 08 48 89 df e8 d1 da
RSP: 0018:ffffc90005d6fae8 EFLAGS: 00010202
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff8238f165
RDX: ffff888026c4a440 RSI: ffffffff8238f40b RDI: 0000000000000005
RBP: 0000000000000000 R08: ffff88805f4fc600 R09: 000000000000001e
R10: 0000000000000000 R11: 0000000000000000 R12: 000000000000002c
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff88805f4fc5fa
FS:  0000000000000000(0000) GS:ffff88806a800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f989f7fd870 CR3: 000000000df7c000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	4c 39 fb             	cmp    %r15,%rbx
   3:	0f 83 25 04 00 00    	jae    0x42e
   9:	e8 e5 94 54 ff       	call   0xff5494f3
   e:	44 8b 2c 24          	mov    (%rsp),%r13d
  12:	41 83 fd 1e          	cmp    $0x1e,%r13d
  16:	0f 87 77 23 00 00    	ja     0x2393
  1c:	4a 8d 44 ed 08       	lea    0x8(%rbp,%r13,8),%rax
  21:	48 89 44 24 30       	mov    %rax,0x30(%rsp)
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 80 3c 30 00       	cmpb   $0x0,(%rax,%r14,1) <-- trapping instruction
  2f:	0f 85 4f 23 00 00    	jne    0x2384
  35:	4a 8b 5c ed 08       	mov    0x8(%rbp,%r13,8),%rbx
  3a:	48 89 df             	mov    %rbx,%rdi
  3d:	e8                   	.byte 0xe8
  3e:	d1 da                	rcr    %edx


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