linux-kernel - Re: [PATCH] NFS: nfsaclsvc_encode_getaclres() - Fix potential NULL deref and tiny optimization.

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Date:	Fri, 27 Oct 2006 14:46:03 -0700 (PDT)
From:	David Rientjes <rientjes@...washington.edu>
To:	Jesper Juhl <jesper.juhl@...il.com>
cc:	linux-kernel@...r.kernel.org, Andreas Gruenbacher <agruen@...e.de>,
	Neil Brown <neilb@....unsw.edu.au>, nfs@...ts.sourceforge.net,
	Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH] NFS: nfsaclsvc_encode_getaclres() - Fix potential NULL
 deref and tiny optimization.

On Fri, 27 Oct 2006, Jesper Juhl wrote:

> In fs/nfsd/nfs2acl.c::nfsaclsvc_encode_getaclres() I see a few issues.
> 
> 1) At the top of the function we assign to the 'inode' variable by 
> dereferencing 'dentry', but further down we test 'dentry' for NULL. So, if 
> 'dentry' (which is really 'resp->fh.fh_dentry') can be NULL, then either 
> we have a potential NULL pointer deref bug or we have a superflous test.
> 

resp->fh.fh_dentry cannot be NULL on nfsaclsvc_encode_getaclres so the 
early assignment is appropriate for both *dentry and *inode.  *inode will 
need to be checked for NULL in the conditional, however, and return 0 on 
true.

> 3) There are two locations in the function where we may return before we 
> use the value of the variable 'w', but we compute it at the very top of the 
> function. So in the case where we return early we have wasted a few cycles 
> computing a value that was never used.
> 

w should be an unsigned int.

		David
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