Re: PANIC: double fault in fixup_bad_iret

[Thomas Gleixner]

Dmitry,

Dmitry Vyukov <dvyukov@xxxxxxxxxx> writes:
> On Fri, May 29, 2020 at 3:14 PM syzbot
> <syzbot+dc1fa714cb070b184db5@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>>
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit:    7b4cb0a4 Add linux-next specific files for 20200525
>> git tree:       linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=15dc34ba100000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=47b0740d89299c10
>> dashboard link: https://syzkaller.appspot.com/bug?extid=dc1fa714cb070b184db5
>> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14678626100000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1017ef06100000
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+dc1fa714cb070b184db5@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> From the reproducer it seems to be either x86 related or ptrace
> related.
>
>> RIP: 0010:fixup_bad_iret+0x24/0x170 arch/x86/kernel/traps.c:665

as a quick assumption that's related to KASAN in fixup_bad_iret() which
is a frightenly bad idea. I'm about to verify.

Thanks,

        tglx