Re: mm: uninterruptable tasks hanged on mmap_sem

[Dmitry Vyukov]

On Tue, Feb 2, 2016 at 10:24 PM, Jiri Kosina <jikos@xxxxxxxxxx> wrote:
> On Tue, 2 Feb 2016, Dmitry Vyukov wrote:
>
>> Original log from fuzzer contained the following WARNING in
>> mm/rmap.c:412. But when I tried to reproduce it, I hit these hanged
>> processes instead. I can't reliably detect what program triggered
>> what. So it may be related, or maybe a separate issue.
>>
>> ------------[ cut here ]------------
>> kernel BUG at mm/rmap.c:412!
>
> Are you by any chance in this test sending signals to the fuzzer?
>
> If so, the bug I just fixed in floppy driver can cause all kinds of memory
> corruptions in case you're running multithreaded accessess to /dev/fd0 and
> sending singals to the threads that are trying to access /dev/fd0 at the
> same time.
>
> Could you please double check that the other floppy fix I've sent you a
> couple days ago doesn't fix this as well? (this test makes sense only if
> signals are involved though).

I have "floppy: fix lock_fdc() signal handling" applied (the final,
second version).
The process is multithreaded and it can well receive SIGKILLs.