[syzbot] general protection fault in hrtimer_start_range_ns

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 835d31d319d9 Merge tag 'media/v5.15-1' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14489886300000
kernel config: https://syzkaller.appspot.com/x/.config?x=d793523866f2daea
dashboard link: https://syzkaller.appspot.com/bug?extid=b935db3fe409625cca1b
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b935db...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 PID: 12936 Comm: iou-sqp-12929 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:lock_hrtimer_base kernel/time/hrtimer.c:173 [inline]
RIP: 0010:hrtimer_start_range_ns+0xc9/0x1ae0 kernel/time/hrtimer.c:1296
Code: 89 9c 24 88 00 00 00 42 80 3c 33 00 74 08 48 89 ef e8 7b 34 5b 00 4c 8b 6d 00 4d 39 fd 0f 84 95 00 00 00 4d 89 ef 49 c1 ef 03 <43> 80 3c 37 00 74 08 4c 89 ef e8 58 34 5b 00 49 8b 7d 00 e8 6f 19
RSP: 0018:ffffc900097af170 EFLAGS: 00010046
RAX: ffff888016d49508 RBX: 1ffff11002da92a7 RCX: ffff888027371c80
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
RBP: ffff888016d49538 R08: ffffffff816fb4b5 R09: 0000000000000003
R10: fffff520012f5e2d R11: 0000000000000004 R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000000000
FS: 00007f7386f28700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000002b5e4000 CR4: 00000000001526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
hrtimer_start include/linux/hrtimer.h:418 [inline]
io_timeout fs/io_uring.c:6120 [inline]
io_issue_sqe+0x53d3/0x9280 fs/io_uring.c:6590
__io_queue_sqe+0xe3/0x1000 fs/io_uring.c:6864
tctx_task_work+0x2ad/0x560 fs/io_uring.c:2143
task_work_run+0x146/0x1c0 kernel/task_work.c:164
tracehook_notify_signal include/linux/tracehook.h:212 [inline]
io_run_task_work+0x110/0x140 fs/io_uring.c:2403
io_sq_thread+0xb5e/0x1220 fs/io_uring.c:7337
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
Modules linked in:
---[ end trace 841fafb7511d53d3 ]---
RIP: 0010:lock_hrtimer_base kernel/time/hrtimer.c:173 [inline]
RIP: 0010:hrtimer_start_range_ns+0xc9/0x1ae0 kernel/time/hrtimer.c:1296
Code: 89 9c 24 88 00 00 00 42 80 3c 33 00 74 08 48 89 ef e8 7b 34 5b 00 4c 8b 6d 00 4d 39 fd 0f 84 95 00 00 00 4d 89 ef 49 c1 ef 03 <43> 80 3c 37 00 74 08 4c 89 ef e8 58 34 5b 00 49 8b 7d 00 e8 6f 19
RSP: 0018:ffffc900097af170 EFLAGS: 00010046
RAX: ffff888016d49508 RBX: 1ffff11002da92a7 RCX: ffff888027371c80
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
RBP: ffff888016d49538 R08: ffffffff816fb4b5 R09: 0000000000000003
R10: fffff520012f5e2d R11: 0000000000000004 R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000000000
FS: 00007f7386f28700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000002b5e4000 CR4: 00000000001526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 89 9c 24 88 00 00 00 mov %ebx,0x88(%rsp)
7: 42 80 3c 33 00 cmpb $0x0,(%rbx,%r14,1)
c: 74 08 je 0x16
e: 48 89 ef mov %rbp,%rdi
11: e8 7b 34 5b 00 callq 0x5b3491
16: 4c 8b 6d 00 mov 0x0(%rbp),%r13
1a: 4d 39 fd cmp %r15,%r13
1d: 0f 84 95 00 00 00 je 0xb8
23: 4d 89 ef mov %r13,%r15
26: 49 c1 ef 03 shr $0x3,%r15
* 2a: 43 80 3c 37 00 cmpb $0x0,(%r15,%r14,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 4c 89 ef mov %r13,%rdi
34: e8 58 34 5b 00 callq 0x5b3491
39: 49 8b 7d 00 mov 0x0(%r13),%rdi
3d: e8 .byte 0xe8
3e: 6f outsl %ds:(%rsi),(%dx)
3f: 19 .byte 0x19


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[Thomas Gleixner]

On Mon, Sep 06 2021 at 03:28, syzbot wrote:
> syzbot found the following issue on:
>
> HEAD commit: 835d31d319d9 Merge tag 'media/v5.15-1' of git://git.kernel..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14489886300000
> kernel config: https://syzkaller.appspot.com/x/.config?x=d793523866f2daea
> dashboard link: https://syzkaller.appspot.com/bug?extid=b935db3fe409625cca1b
> compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b935db...@syzkaller.appspotmail.com
>
> general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> CPU: 0 PID: 12936 Comm: iou-sqp-12929 Not tainted 5.14.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:lock_hrtimer_base kernel/time/hrtimer.c:173 [inline]

That's almost certainly deferencing hrtimer->base and as that is NULL this looks
like a not initialized hrtimer.

Jens?

[Jens Axboe]

On 9/8/21 10:45 AM, Thomas Gleixner wrote:
> On Mon, Sep 06 2021 at 03:28, syzbot wrote:
>> syzbot found the following issue on:
>>
>> HEAD commit: 835d31d319d9 Merge tag 'media/v5.15-1' of git://git.kernel..
>> git tree: upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=14489886300000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=d793523866f2daea
>> dashboard link: https://syzkaller.appspot.com/bug?extid=b935db3fe409625cca1b
>> compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
>>
>> Unfortunately, I don't have any reproducer for this issue yet.
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+b935db...@syzkaller.appspotmail.com
>>
>> general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
>> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
>> CPU: 0 PID: 12936 Comm: iou-sqp-12929 Not tainted 5.14.0-syzkaller #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>> RIP: 0010:lock_hrtimer_base kernel/time/hrtimer.c:173 [inline]
>
> That's almost certainly deferencing hrtimer->base and as that is NULL
> this looks like a not initialized hrtimer.

Does certainly look like that, I'll take a look. And agree the next one
looks like the same thing.

--
Jens Axboe

[Jens Axboe]

I think both are fallout from a regression that we had in linked
requests, where we'd queue requests that weren't fully prepared. Current
Linus -git should not have this problem:

These were the two related fixes:

io_uring: fix queueing half-created requests
io_uring: don't submit half-prepared drain request

--
Jens Axboe

[Thomas Gleixner]

Makes sense and the backtraces in the changelogs point at the same class
of problem.

Thanks,

tglx

[syzbot]

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