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

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Date:	Wed, 16 Apr 2008 14:11:31 -0400
From:	Trond Myklebust <trond.myklebust@....uio.no>
To:	Cyrill Gorcunov <gorcunov@...il.com>
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


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);
> 

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