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

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Message-Id: <200609261317.k8QDHRVG013833@turing-police.cc.vt.edu>
Date:	Tue, 26 Sep 2006 09:17:26 -0400
From:	Valdis.Kletnieks@...edu
To:	Eric Sesterhenn <snakebyte@....de>
Cc:	linux-kernel@...r.kernel.org, chuck.lever@...cle.com
Subject: Re: [Patch] Possible dereference in fs/nfsd/nfs4callback.c

On Tue, 26 Sep 2006 12:30:59 +0200, Eric Sesterhenn said:

> we set cb->cb_client to NULL and pass it to rpc_shutdown_client() which dereferences it.
> The easy fix below.

>  out_clnt:
> -	rpc_shutdown_client(cb->cb_client);
> +	if (cb->cb_client)
> +		rpc_shutdown_client(cb->cb_client);

OK, I admit not knowing the NFS code well, but this one looks suspiciously
like "easy paper-over" rather than "easy fix".  Is there other cod elsewhere
that guards this case from ever actually happening?  If it *does* happen,
is it indicative of major borkage and we really should do something like:

	if (cb->cb_client)
		rpm_shutdown_client(cb->cb_client)
	else
		printk(KERN_ERR "Yowza - trashed NFS control structures...");

or even maybe a more drastic action (oops/panic)?

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