[syzbot] [fs?] [io-uring?] general protection fault in __ep_remove

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 480e035fc4c7 Merge tag 'drm-next-2024-03-13' of https://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15f55413180000
kernel config: https://syzkaller.appspot.com/x/.config?x=1e5b814e91787669
dashboard link: https://syzkaller.appspot.com/bug?extid=045b454ab35fd82a35fb
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=101db623180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10801175180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5f73b6ef963d/disk-480e035f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/46c949396aad/vmlinux-480e035f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e3b4d0f5a5f8/bzImage-480e035f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+045b45...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 PID: 5075 Comm: syz-executor119 Not tainted 6.8.0-syzkaller-08073-g480e035fc4c7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
RIP: 0010:__ep_remove+0x13a/0x780 fs/eventpoll.c:825
Code: 89 e7 49 c1 ef 03 41 80 3c 2f 00 74 08 4c 89 e7 e8 8b 81 d9 ff 4d 8b 34 24 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 4c 89 f7 e8 68 81 d9 ff 49 8b 1e 48 8b 04 24 48
RSP: 0018:ffffc90003b6fa78 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000001 RCX: dffffc0000000000
RDX: ffff88807a310000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffffffff821ec2a4 R09: fffff5200076df40
R10: dffffc0000000000 R11: fffff5200076df40 R12: ffff88802916cbb8
R13: ffff88802916ca00 R14: 0000000000000000 R15: 1ffff1100522d977
FS: 00007f034c6ff6c0(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000004 CR3: 00000000775ec000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
eventpoll_release_file+0xdb/0x1c0 fs/eventpoll.c:1071
eventpoll_release include/linux/eventpoll.h:53 [inline]
__fput+0x6d7/0x8a0 fs/file_table.c:413
task_work_run+0x24f/0x310 kernel/task_work.c:180
get_signal+0x1673/0x1850 kernel/signal.c:2683
arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop kernel/entry/common.c:105 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:201 [inline]
syscall_exit_to_user_mode+0xc9/0x360 kernel/entry/common.c:212
do_syscall_64+0x10a/0x240 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f034c84c059
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 1f 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f034c6ff178 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f034c8f0038 RCX: 00007f034c84c059
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f034c8f0038
RBP: 00007f034c8f0030 R08: 00007f034c6ff6c0 R09: 00007f034c6ff6c0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f034c8f003c
R13: 0000000000000002 R14: 00007f034c9ffc40 R15: 00007f034c9ffd28
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__ep_remove+0x13a/0x780 fs/eventpoll.c:825
Code: 89 e7 49 c1 ef 03 41 80 3c 2f 00 74 08 4c 89 e7 e8 8b 81 d9 ff 4d 8b 34 24 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 4c 89 f7 e8 68 81 d9 ff 49 8b 1e 48 8b 04 24 48
RSP: 0018:ffffc90003b6fa78 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000001 RCX: dffffc0000000000
RDX: ffff88807a310000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffffffff821ec2a4 R09: fffff5200076df40
R10: dffffc0000000000 R11: fffff5200076df40 R12: ffff88802916cbb8
R13: ffff88802916ca00 R14: 0000000000000000 R15: 1ffff1100522d977
FS: 00007f034c6ff6c0(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000004 CR3: 00000000775ec000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 89 e7 mov %esp,%edi
2: 49 c1 ef 03 shr $0x3,%r15
6: 41 80 3c 2f 00 cmpb $0x0,(%r15,%rbp,1)
b: 74 08 je 0x15
d: 4c 89 e7 mov %r12,%rdi
10: e8 8b 81 d9 ff call 0xffd981a0
15: 4d 8b 34 24 mov (%r12),%r14
19: 4c 89 f0 mov %r14,%rax
1c: 48 c1 e8 03 shr $0x3,%rax
20: 48 b9 00 00 00 00 00 movabs $0xdffffc0000000000,%rcx
27: fc ff df
* 2a: 80 3c 08 00 cmpb $0x0,(%rax,%rcx,1) <-- trapping instruction
2e: 74 08 je 0x38
30: 4c 89 f7 mov %r14,%rdi
33: e8 68 81 d9 ff call 0xffd981a0
38: 49 8b 1e mov (%r14),%rbx
3b: 48 8b 04 24 mov (%rsp),%rax
3f: 48 rex.W


---
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[Jens Axboe]

This isn't related to io_uring at all, not sure why syzbot has this idea
that anything that involves task_work is iouring.

#syz set subsystems: fs

--
Jens Axboe

[Pavel Begunkov]

On 4/15/24 15:31, Jens Axboe wrote:
> This isn't related to io_uring at all, not sure why syzbot has this idea
> that anything that involves task_work is iouring.

The repro does send an IORING_OP_READ, but I haven't looked deeper
to say if it's anything meaningful.

> #syz set subsystems: fs
>

--

Pavel Begunkov