[moderation] [block?] general protection fault in loop_process_work

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4f6b6c2b2f86 Merge tag 'riscv-for-linus-6.5-mw2' of git://..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=115fa4a8a80000
kernel config: https://syzkaller.appspot.com/x/.config?x=7df0cabaf5becfdc
dashboard link: https://syzkaller.appspot.com/bug?extid=1e0c0f6fa11e5acdd9af
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
CC: [ax...@kernel.dk linux...@vger.kernel.org linux-...@vger.kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c1fd3f788fef/disk-4f6b6c2b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7a2431af692d/vmlinux-4f6b6c2b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0e1d6ad5f69e/bzImage-4f6b6c2b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1e0c0f...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000032: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000190-0x0000000000000197]
CPU: 1 PID: 8868 Comm: kworker/u4:12 Not tainted 6.4.0-syzkaller-12316-g4f6b6c2b2f86 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
Workqueue: loop3 loop_workfn
RIP: 0010:lo_write_bvec drivers/block/loop.c:248 [inline]
RIP: 0010:lo_write_simple drivers/block/loop.c:271 [inline]
RIP: 0010:do_req_filebacked drivers/block/loop.c:495 [inline]
RIP: 0010:loop_handle_cmd drivers/block/loop.c:1886 [inline]
RIP: 0010:loop_process_work+0x101c/0x20a0 drivers/block/loop.c:1921
Code: 01 00 00 00 be 01 00 00 00 48 8b 54 24 48 48 8b 7c 24 18 48 8b 68 60 e8 92 57 e6 fe 4c 8d a5 90 01 00 00 4c 89 e0 48 c1 e8 03 <42> 80 3c 38 00 0f 85 5e 0c 00 00 4c 8b b5 90 01 00 00 4c 89 f0 48
RSP: 0018:ffffc9000530fb30 EFLAGS: 00010212
RAX: 0000000000000032 RBX: 0000000000001000 RCX: 0000000000000000
RDX: 1ffff92000a61f93 RSI: 1ffff92000a61f01 RDI: ffffc9000530fc98
RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000190
R13: ffffea0000a86f40 R14: 0000000000000000 R15: dffffc0000000000
FS: 0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555558d3848 CR3: 000000007bb2c000 CR4: 0000000000350ee0
Call Trace:
<TASK>
process_one_work+0xa34/0x16f0 kernel/workqueue.c:2597
worker_thread+0x67d/0x10c0 kernel/workqueue.c:2748
kthread+0x344/0x440 kernel/kthread.c:389
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:lo_write_bvec drivers/block/loop.c:248 [inline]
RIP: 0010:lo_write_simple drivers/block/loop.c:271 [inline]
RIP: 0010:do_req_filebacked drivers/block/loop.c:495 [inline]
RIP: 0010:loop_handle_cmd drivers/block/loop.c:1886 [inline]
RIP: 0010:loop_process_work+0x101c/0x20a0 drivers/block/loop.c:1921
Code: 01 00 00 00 be 01 00 00 00 48 8b 54 24 48 48 8b 7c 24 18 48 8b 68 60 e8 92 57 e6 fe 4c 8d a5 90 01 00 00 4c 89 e0 48 c1 e8 03 <42> 80 3c 38 00 0f 85 5e 0c 00 00 4c 8b b5 90 01 00 00 4c 89 f0 48
RSP: 0018:ffffc9000530fb30 EFLAGS: 00010212
RAX: 0000000000000032 RBX: 0000000000001000 RCX: 0000000000000000
RDX: 1ffff92000a61f93 RSI: 1ffff92000a61f01 RDI: ffffc9000530fc98
RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000190
R13: ffffea0000a86f40 R14: 0000000000000000 R15: dffffc0000000000
FS: 0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7bc6ffb000 CR3: 000000002f8b6000 CR4: 0000000000350ef0
----------------
Code disassembly (best guess):
0: 01 00 add %eax,(%rax)
2: 00 00 add %al,(%rax)
4: be 01 00 00 00 mov $0x1,%esi
9: 48 8b 54 24 48 mov 0x48(%rsp),%rdx
e: 48 8b 7c 24 18 mov 0x18(%rsp),%rdi
13: 48 8b 68 60 mov 0x60(%rax),%rbp
17: e8 92 57 e6 fe callq 0xfee657ae
1c: 4c 8d a5 90 01 00 00 lea 0x190(%rbp),%r12
23: 4c 89 e0 mov %r12,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1) <-- trapping instruction
2f: 0f 85 5e 0c 00 00 jne 0xc93
35: 4c 8b b5 90 01 00 00 mov 0x190(%rbp),%r14
3c: 4c 89 f0 mov %r14,%rax
3f: 48 rex.W


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the bug is already fixed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to change bug's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the bug is a duplicate of another bug, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.