Re: [uml-devel] WARNING: at mm/mmap.c:2757 exit_mmap+0x161/0x170()

["Toralf Förster" <toralf.foerster@gmx.de>]

On 05/15/2013 09:11 PM, richard -rw- weinberger wrote:
> On Wed, May 15, 2013 at 9:06 PM, Toralf Förster <toralf.foerster@gmx.de> wrote:
>> On 05/13/2013 09:12 AM, richard -rw- weinberger wrote:
>>> This looks like another issue.
>>> Are you testing process_vm_writev() with trinity?
>>> Looks like it managed to overwrite the stub page of a process, which
>>> is not good.
>> nope, it is the mremap syscall.
>>
>> A command like
>>
>> $>trinity -c mremap -N 10
>>
>> immediately after starting a 32 bit Gentoo linux guest with current kernel 3.10-rc1-... +
>> strnlen + stub4 patch works, but later a
>>
>> $>trinity -c mremap -N 1000
>>
>> yields into
>>
>> 2013-05-15T21:02:04.061+02:00 trinity kernel: Stub registers -
>> 2013-05-15T21:02:04.061+02:00 trinity kernel:   0 - 100000
>> 2013-05-15T21:02:04.061+02:00 trinity kernel:   1 - 300000
>> 2013-05-15T21:02:04.061+02:00 trinity kernel:   2 - 0
>> 2013-05-15T21:02:04.061+02:00 trinity kernel:   3 - 0
>> 2013-05-15T21:02:04.061+02:00 trinity kernel:   4 - 0
>> 2013-05-15T21:02:04.061+02:00 trinity kernel:   5 - 0
>> 2013-05-15T21:02:04.061+02:00 trinity kernel:   6 - 0
>> 2013-05-15T21:02:04.061+02:00 trinity kernel:   7 - 7b
>> 2013-05-15T21:02:04.061+02:00 trinity kernel:   8 - 7b
>> 2013-05-15T21:02:04.065+02:00 trinity kernel:   9 - 0
>> 2013-05-15T21:02:04.065+02:00 trinity kernel:   10 - 33
>> 2013-05-15T21:02:04.065+02:00 trinity kernel:   11 - ffffffff
>> 2013-05-15T21:02:04.065+02:00 trinity kernel:   12 - 1000c3
>> 2013-05-15T21:02:04.065+02:00 trinity kernel:   13 - 73
>> 2013-05-15T21:02:04.065+02:00 trinity kernel:   14 - 10206
>> 2013-05-15T21:02:04.065+02:00 trinity kernel:   15 - 101028
>> 2013-05-15T21:02:04.065+02:00 trinity kernel:   16 - 7b
>> 2013-05-15T21:02:04.065+02:00 trinity kernel: wait_stub_done : failed to wait for SIGTRAP, pid = 15692, n = 15692, errno = 0, status = 0xb7f
>>
>> and now that process can't be killed - I had to stop the UML guest.
> 
> Hmm, you've remapped the stub page and therefore the process broke.
> I think it would make sense to kill the process in stead of writing
> the "wait_stub_done ..." message.
> Changing the stub page is as destructive than overwriting the stack.

Unfortunately no trinity process can be killed as soon as that happen.
Neither pgrep, pkill, nor "ps -efla" do return any result.
Killing any of those processes by its pid won't work too.

> Maybe we can teach triniy to no change the stub page.
> I'm sure trinity has also a mechanism to not destroy the stack.

@trinity Mailing list
	What do you think about that ?

-- 
MfG/Sincerely
Toralf Förster
pgp finger print: 7B1A 07F4 EC82 0F90 D4C2 8936 872A E508 7DB6 9DA3