lkml.org 
[lkml]   [2014]   [Nov]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] ipc,sem block sem_lock on sma->lock during sma initialization
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 11/21/2014 03:09 PM, Andrew Morton wrote:
> On Fri, 21 Nov 2014 14:52:26 -0500 Rik van Riel <riel@redhat.com>
> wrote:
>
>> When manipulating just one semaphore with semop, sem_lock only
>> takes that single semaphore's lock. This creates a problem during
>> initialization of the semaphore array, when the data structures
>> used by sem_lock have not been set up yet. The sma->lock is
>> already held by newary, and we just have to make sure everything
>> else waits on that lock during initialization.
>>
>> Luckily it is easy to make sem_lock wait on the sma->lock, by
>> pretending there is a complex operation in progress while the sma
>> is being initialized.
>>
>> The newary function already zeroes sma->complex_count before
>> unlocking the sma->lock.
>
> What are the runtime effects of the bug?
>

NULL pointer dereference in spin_lock from sem_lock,
if it is called before sma->sem_base has been pointed
somewhere valid.

- --
All rights reversed
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1

iQEcBAEBAgAGBQJUb6CnAAoJEM553pKExN6Dh8oH/iFVqwrukMkZp7ViFTC84DVK
m8rw6CWk76kEvi6BWx977nT26e7ZfiOCxrhyy/gETOnUDJMgQrn7cFMFd6Ja/2yG
uGCq5WcvVLDiLw7ij9Rqu4C6aHcICserzgfXwWV0XAa5TZOEqvg6FKZgCUHN6sxM
ek0TV0oq/VQvRwAQk/MFDOv38PydH2LH1Z3wXk7JVlhEMX062a4EoxTAe8Teed2p
X5+mTOl4jezog2rFJxFe0Cp8PxpqAi4f1kDugQKohZ3TpUFqH4VKZYmTtvHvpNDH
oeHjnRv632N8KuU2lvIi7EGJGu0Y+ReyOr+NQtozlRYCTPuY/rezkbBmgVwu4iY=
=CDvy
-----END PGP SIGNATURE-----


\
 
 \ /
  Last update: 2014-11-21 22:21    [W:0.118 / U:27.816 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site