linux-kernel - Re: [patch 1/3] NFS: fix potential NULL pointer dereference

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Message-ID: <20080416181336.GA7657@cvg>
Date:	Wed, 16 Apr 2008 22:13:36 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Trond Myklebust <trond.myklebust@....uio.no>
Cc:	bfields@...ldses.org, neilb@...e.de, ibm-acpi@....eng.br,
	len.brown@...el.com, kkeil@...e.de, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 1/3] NFS: fix potential NULL pointer dereference

[Trond Myklebust - Wed, Apr 16, 2008 at 02:11:31PM -0400]
| 
| On Wed, 2008-04-16 at 21:44 +0400, Cyrill Gorcunov wrote:
| > plain text document attachment (nfs-kstrdup-nul-fix)
| > It's possible to get NULL pointer dereference
| > if kstrndup failed
| > 
| > Here is a possible scenario
| > 
| > nfs4_get_sb
| >   nfs4_validate_mount_data
| >     o kstrndup failed so args->nfs_server.export_path = NULL
| >   nfs4_create_server
| >     nfs4_path_walk(..., NULL) -> Oops!
| > 
| > Signed-off-by: Cyrill Gorcunov <gorcunov@...il.com>
| 
| Why fix only the one case? What about the other kstrdup/kstrndup cases
| in super.c that appear to be unchecked?
| 
| Trond
| 
| > ---
| > 
| > Index: linux-2.6.git/fs/nfs/super.c
| > ===================================================================
| > --- linux-2.6.git.orig/fs/nfs/super.c	2008-04-15 23:01:30.000000000 +0400
| > +++ linux-2.6.git/fs/nfs/super.c	2008-04-16 20:01:44.000000000 +0400
| > @@ -1858,6 +1858,8 @@ static int nfs4_validate_mount_data(void
| >  		if (len > NFS4_MAXPATHLEN)
| >  			return -ENAMETOOLONG;
| >  		args->nfs_server.export_path = kstrndup(c, len, GFP_KERNEL);
| > +		if (!args->nfs_server.export_path)
| > +			return -ENOMEM;
| >  
| >  		dprintk("NFS: MNTPATH: '%s'\n", args->nfs_server.export_path);
| > 
| 

This one is leading to NULL deref, others - don't

		- Cyrill -
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