linux-kernel - Re: [PATCH] Fix for possible null pointer dereference in auth.c

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Message-ID: <CAFo99ga5hw+KLT+5gY5sArsykUnBY9fZSvZaSnK54S5HW-nZHw@mail.gmail.com>
Date:	Fri, 16 May 2014 00:10:53 +0200
From:	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>
To:	Trond Myklebust <trond.myklebust@...marydata.com>
Cc:	"J. Bruce Fields" <bfields@...ldses.org>,
	"David S. Miller" <davem@...emloft.net>, linux-nfs@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix for possible null pointer dereference in auth.c

Hi

I do not know, I'm not an expert on this code.
But since there before was a if (cred) someone must have thought this
could happen.

Best regards
Rickard Strandqvist


2014-05-16 0:07 GMT+02:00 Trond Myklebust <trond.myklebust@...marydata.com>:
> On Thu, May 15, 2014 at 5:56 PM, Rickard Strandqvist
> <rickard_strandqvist@...ctrumdigital.se> wrote:
>> There is otherwise a risk of a possible null pointer dereference.
>>
>> Was largely found by using a static code analysis program called cppcheck.
>>
>> Signed-off-by: Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>
>> ---
>>  net/sunrpc/auth.c |   10 +++++++---
>>  1 fil ändrad, 7 tillägg(+), 3 borttagningar(-)
>>
>> diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
>> index 5285ead..3a55698 100644
>> --- a/net/sunrpc/auth.c
>> +++ b/net/sunrpc/auth.c
>> @@ -801,10 +801,14 @@ rpcauth_invalcred(struct rpc_task *task)
>>  {
>>         struct rpc_cred *cred = task->tk_rqstp->rq_cred;
>>
>> -       dprintk("RPC: %5u invalidating %s cred %p\n",
>> -               task->tk_pid, cred->cr_auth->au_ops->au_name, cred);
>> -       if (cred)
>> +       if (cred) {
>> +               dprintk("RPC: %5u invalidating %s cred %p\n",
>> +                       task->tk_pid, cred->cr_auth->au_ops->au_name, cred);
>> +
>>                 clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
>> +       }
>> +       else
>> +               dprintk("RPC: %5u invalidating is NULL\n", task->tk_pid);
>>  }
>>
>>
>
> Can you please explain how we can get to rpcauth_invalcred() without a
> valid cred pointer? I'm not seeing it...
>
> Cheers
>   Trond
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