linux-kernel - Re: [Patch] Possible dereference in fs/nfsd/nfs4callback.c

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Date:	Tue, 26 Sep 2006 08:58:56 -0400
From:	Chuck Lever <chuck.lever@...cle.com>
To:	Eric Sesterhenn <snakebyte@....de>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [Patch] Possible dereference in fs/nfsd/nfs4callback.c

Eric Sesterhenn wrote:
> hi,
> 
> the following commit introduced a possible NULL pointer dereference
> http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=ae5c79476f36512d1100e162606bb5691f2cce5a
> 
> we set cb->cb_client to NULL and pass it to rpc_shutdown_client() which dereferences it.

What was I thinking/smoking?  ;-)

> The easy fix below.
> 
> Signed-off-by: Eric Sesterhenn <snakebyte@....de>
> 
> --- linux-2.6.18-git5/fs/nfsd/nfs4callback.c.orig	2006-09-26 12:24:23.000000000 +0200
> +++ linux-2.6.18-git5/fs/nfsd/nfs4callback.c	2006-09-26 12:24:40.000000000 +0200
> @@ -450,7 +450,8 @@ out_rpciod:
>  	rpciod_down();
>  	cb->cb_client = NULL;
>  out_clnt:
> -	rpc_shutdown_client(cb->cb_client);
> +	if (cb->cb_client)
> +		rpc_shutdown_client(cb->cb_client);
>  out_err:
>  	dprintk("NFSD: warning: no callback path to client %.*s\n",
>  		(int)clp->cl_name.len, clp->cl_name.data);

Actually I see another problem here.

rpc_create() doesn't return NULL, it returns an ERR_PTR.  So the return 
code check in the code just before this is also bogus.

I'll send a complete fix through Trond.
-
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