linux-ext4 - Re: Oops with ext(3|4) and audit and Xen

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Message-ID: <CALnj_=70B2O9RuNEnb3irsvNbaxrAD1GevYRdU0zw6c8=g1Syw@mail.gmail.com>
Date:	Mon, 8 Oct 2012 14:19:05 -0700
From:	Peter Moody <pmoody@...gle.com>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: Oops with ext(3|4) and audit and Xen

On Mon, Oct 8, 2012 at 2:15 PM, Theodore Ts'o <tytso@....edu> wrote:
> On Mon, Oct 08, 2012 at 11:19:53AM -0700, Peter Moody wrote:
>>
>> I'm trying to track down a BUG() that seems to strike a particular
>> system configuration (unfortunately, an increasingly common
>> configuration), but does so with 100% reliability.
>
> Peter, this looks like exactly the same issue that you asked me about
> back in July, isn't it?  Check your corp e-mail archives for the
> subject line: "advice/pointers on debugging a potential kernel race".
>
> As I recall, the problem was a missing path_put() in audit_putname()
> in kernel/auditsc.c?
>
>                                         - Ted

Yep, this is that issue and I thought that was the fix but it turns
out it wasn't. The dentry was already being pinned in:

if (!context->pwd.dentry)
  get_fs_pwd(current->fs, &context->pwd);

so my path_get/path_put patch just needlessly grabbed a second reference.

-- 
Peter Moody      Google    1.650.253.7306
Security Engineer  pgp:0xC3410038
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