From: Mark Tinguely <tinguely@sgi.com>
To: Eric Sandeen <sandeen@sandeen.net>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH] xfs: shutdown filesystem if xfs_perag_get fails
Date: Mon, 22 Apr 2013 08:45:02 -0500 [thread overview]
Message-ID: <51753EDE.6000301@sgi.com> (raw)
In-Reply-To: <5174603A.8030208@sandeen.net>
On 04/21/13 16:55, Eric Sandeen wrote:
> On 4/21/13 12:41 PM, Mark Tinguely wrote:
>
>> This problem happened locally with a bad inode number from xfs
>> recovery. xfs_perag_get() can return NULL if given a bad agno.
>> Most callers of xfs_perag_get() do not check for a NULL before
>> using the pointer. This patch forces a shutdown of the filesystem
>> for those callers that do not check the return value rather than
>> crashing on a dereferenced NULL pointer.
>
> Hi Mark -
>
> I'm curious, what was the callchain when this happened? Was it
> during recovery? If so, would aborting recovery be more prudent?
>
> I might be missing something, but I'm not sure how shutting
> down avoids a subsequent null ptr deref& crash.
>
> i.e. if a caller does something like:
>
> pag = xfs_perag_get(mp, agno);
> spin_lock(&pag->pagb_lock);
>
> shutting down in xfs_perag_get doesn't save us from a
> null pag pointer, would it?
>
> Thanks,
> -Eric
You are correct, we have to exit the routine(s) to avoid the
dereference. Let the callers handle the error.
Sorry for the noise.
--Mark.
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next prev parent reply other threads:[~2013-04-22 13:45 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20130419204102.736961610@sgi.com>
2013-04-21 17:41 ` [PATCH] xfs: shutdown filesystem if xfs_perag_get fails Mark Tinguely
2013-04-21 21:55 ` Eric Sandeen
2013-04-22 13:45 ` Mark Tinguely [this message]
2013-04-22 14:32 ` Eric Sandeen
2013-04-22 15:11 ` Mark Tinguely
2013-04-22 23:30 ` Dave Chinner
2013-04-23 13:48 ` Mark Tinguely
2013-04-23 15:54 ` Chandra Seetharaman
2013-04-23 20:49 ` Dave Chinner
2013-04-25 22:41 ` Chandra Seetharaman
2013-04-26 1:32 ` Dave Chinner
2013-04-26 15:32 ` Mark Tinguely
2013-04-26 16:07 ` Ben Myers
2013-04-29 22:30 ` Dave Chinner
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