Re: cxgb4: Missing NULL check of the return value of get_skb() in function send_flowc()

From: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
To: Roland Dreier <roland-BHEL68pLQRGGvPXPguhicg@public.gmane.org>
Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: cxgb4: Missing NULL check of the return value of get_skb() in function send_flowc()
Date: Fri, 13 Jul 2012 08:38:07 -0500	[thread overview]
Message-ID: <500024BF.3090403@opengridcomputing.com> (raw)
In-Reply-To: <CAL1RGDWwXxr_2WDvTTwW41fYP-+gfqf=DzB3cF-Aoe=DS74JJg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On 7/13/2012 12:03 AM, Roland Dreier wrote:
> steve, in case you didn't read this because of the generic subject:

Thanks Roland.  Yes, I missed this.  I'll get to this asap...

> On Thu, Jul 12, 2012 at 7:16 PM,  <bugzilla-daemon-590EEB7GvNiWaY/ihj7yzEB+6BGkLq7r@public.gmane.org> wrote:
>> https://bugzilla.kernel.org/show_bug.cgi?id=44631
>>
>>             Summary: Missing NULL check of the return value of get_skb() in
>>                      function send_flowc()
>>             Product: Drivers
>>             Version: 2.5
>>      Kernel Version: 2.6.39
>>            Platform: All
>>          OS/Version: Linux
>>                Tree: Mainline
>>              Status: NEW
>>            Severity: normal
>>            Priority: P1
>>           Component: Infiniband/RDMA
>>          AssignedTo: drivers_infiniband-rdma-ztI5WcYan/vQLgFONoPN62D2FQJk+8+b@public.gmane.org
>>          ReportedBy: rucsoftsec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
>>          Regression: No
>>
>>
>> Function get_skb() may return a NULL pointer, and its return value shall be
>> checked before used. But in function send_flowc() after get_skb() is called(at
>> drivers/infiniband/hw/cxgb4/cm.c:362), the return value is immediately used as
>> a parameter of __skb_put() without NULL check. Besides, there is no check
>> before the parameter is dereferenced in the callee function __skb_put(). So an
>> invalid memory access may be triggered.
>> The related code snippets in send_flowc() are as following.
>> send_flowc() @@drivers/infiniband/hw/cxgb4/cm.c:362
>>   362        skb = get_skb(skb, flowclen, GFP_KERNEL);
>>   363        flowc = (struct fw_flowc_wr *)__skb_put(skb, flowclen);
>>
>> And the implementation of get_skb() are as following.
>> get_skb() drivers/infiniband/hw/cxgb4/cm.c:301
>>   301static struct sk_buff *get_skb(struct sk_buff *skb, int len, gfp_t gfp)
>>   302{
>>   303        if (skb && !skb_is_nonlinear(skb) && !skb_cloned(skb)) {
>>   304                skb_trim(skb, 0);
>>   305                skb_get(skb);
>>   306                skb_reset_transport_header(skb);
>>   307        } else {
>>   308                skb = alloc_skb(len, gfp);
>>   309        }
>>   310        return skb;
>>   311}
>>
>> Following is a call instance of snd_flowc.
>> act_establish @@drivers/infiniband/hw/cxgb4/cm.c:695
>>   695        /* start MPA negotiation */
>>   696        send_flowc(ep, NULL);
>>
>> So from the source code we can see that potential NULL dereference fault exists
>> when path act_establish()->send_flowc()->get_skb()->alloc_skb() is executed.
>>
>> Thank you
>>
>> RUC_Soft_Sec
>>
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