linux-hardening - Re: [PATCH][next] powerpc/vas: Fix potential NULL pointer dereference

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Date:   Tue, 26 Oct 2021 13:42:01 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Tyrel Datwyler <tyreld@...ux.ibm.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Haren Myneni <haren@...ux.ibm.com>,
        linux-hardening@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] powerpc/vas: Fix potential NULL pointer dereference

On Mon, Oct 18, 2021 at 02:09:31PM -0700, Tyrel Datwyler wrote:
> On 10/14/21 10:03 PM, Gustavo A. R. Silva wrote:
> > (!ptr && !ptr->foo) strikes again. :)
> > 
> > The expression (!ptr && !ptr->foo) is bogus and in case ptr is NULL,
> > it leads to a NULL pointer dereference: ptr->foo.
> > 
> > Fix this by converting && to ||
> > 
> > This issue was detected with the help of Coccinelle, and audited and
> > fixed manually.
> > 
> > Fixes: 1a0d0d5ed5e3 ("powerpc/vas: Add platform specific user window operations")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> Looking at the usage pattern it is obvious that if we determine !ptr attempting
> to also confirm !ptr->ops is going to blow up.
> 
> LGTM.
> 
> Reviewed-by: Tyrel Datwyler <tyreld@...ux.ibm.com>

I think I'll take this in my tree.

Thanks, Tyrel.
--
Gustavo