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SubjectRe: 3.0.0-rc2-git1 -- BUG: sleeping function called from invalid context at mm/slub.c:847
On 06/08/2011 02:34 PM, David Rientjes wrote:
> On Wed, 8 Jun 2011, Matt Mackall wrote:
>
>>> Not sure why this ever actually worked with apparmor if prepare_creds()
>>> does an unconditional GFP_KERNEL allocation since this codepath hasn't
>>> changed in at least a year and we're holding a spinlock from setrlimit.
>>> John?
>>
>> Probably a lack of people enabling (and using!) both apparmor and
>> might_sleep. I don't this would be caught by a randconfig boot test.
>>
>
> Right, CONFIG_DEBUG_SPINLOCK_SLEEP isn't enabled by default even though
> CONFIG_DEBUG_KERNEL is. We should probably just allow prepare_creds() to
> take a gfp_t argument just like security_prepare_creds() and change
> existing callers to use GFP_KERNEL with the exception of those using
> setrlimit where we're always holding the spinlock.
>
> Documentation/security/credentials.txt says this:
>
> To alter the current process's credentials, a function should first prepare a
> new set of credentials by calling:
>
> struct cred *prepare_creds(void);
>
> this locks current->cred_replace_mutex and then allocates and constructs a
> duplicate of the current process's credentials, returning with the mutex still
> held if successful. It returns NULL if not successful (out of memory).
>
> although that mutex doesn't exist. David, any downsides to passing the
> gfp_t into prepare_creds()?

Well it certainly isn't needed for the apparmor case, as the bug is being
triggered by how apparmor handles policy replacement, and we have a means
of handling that for atomic contexts.


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