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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        Tyrel Datwyler <tyreld@linux.ibm.com>
Cc:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Nicholas Piggin <npiggin@gmail.com>,
        Haren Myneni <haren@linux.ibm.com>,
        linux-hardening@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH][next] powerpc/vas: Fix potential NULL pointer dereference
In-Reply-To: <20211026184201.GB1457721@embeddedor>
References: <20211015050345.GA1161918@embeddedor>
 <97c42e43-15b9-5db6-d460-dbb16f31954d@linux.ibm.com>
 <20211026184201.GB1457721@embeddedor>
Date:   Wed, 27 Oct 2021 09:30:53 +1100
Message-ID: <87h7d3beqq.fsf@mpe.ellerman.id.au>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

"Gustavo A. R. Silva" <gustavoars@kernel.org> writes:
> 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@vger.kernel.org
>> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.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@linux.ibm.com>
>
> I think I'll take this in my tree.

I've already put it in powerpc/next:

  https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?h=next&id=61cb9ac66b30374c7fd8a8b2a3c4f8f432c72e36

If you need to pick it up as well for some reason that's fine.

cheers