Re: [PATCH] audit: grab a reference to context->pwd when it's cached

Peter Moody
2012-08-20T17:19:45Z

Hi Al,

Any word on a less unpleasant fix? Also, do you know if/how I could
measure the impact of the cacheline bouncing? I haven't been able to
notice anything anecdotally on the machine running this patch, but I'm
not pushing it incredibly hard.

Cheers,
peter

On Wed, Aug 15, 2012 at 6:41 PM, Peter Moody <pmoody@google.com> wrote:
> On Wed, Aug 15, 2012 at 6:26 PM, Alexander Viro <aviro@redhat.com> wrote:
>> On Wed, Aug 15, 2012 at 06:13:33PM -0700, Peter Moody wrote:
>>> On certain systems, in certain pathalogical cases, current's cwd can
>>> be deleted while we're still processing a syscall. This should prevent
>>> the system from evicting the inode while we're still referencing it.
>>>
>>> This seems to fix the bug I reported here:
>>> https://www.redhat.com/archives/linux-audit/2012-August/msg00017.html
>>
>> Sigh... The bug is real, but I really don't like the fix. Among other
>> things, it's going to cause cacheline bouncing from hell and not everyone
>> runs with audit sensibly disabled... Let me think for a while and see
>> if I can come up with something less unpleasant, OK?
>
> Works for me. I have a set of machines that I can very easily test a fix on.
>
> Cheers,
> peter
>
> --
> Peter Moody Google 1.650.253.7306
> Security Engineer pgp:0xC3410038