Re: net: llc: NULL ptr deref in llc_ui_sendmsg

[Sasha Levin]

On 06/06/2014 11:42 AM, Dave Jones wrote:
> On Fri, Jun 06, 2014 at 11:08:33AM -0400, Sasha Levin wrote:
>  > Hi all,
>  > 
>  > While fuzzing with trinity inside a KVM tools guest running the latest -next
>  > kernel I've stumbled on the following spew:
>  > 
>  > [  269.531162] BUG: unable to handle kernel NULL pointer dereference at 000000000000021e
>  > [  269.531217] IP: llc_ui_sendmsg (net/llc/af_llc.c:912)
> 
>  905         /* must bind connection to sap if user hasn't done it. */
>  906         if (sock_flag(sk, SOCK_ZAPPED)) {
>  907                 /* bind to sap with null dev, exclusive. */
>  908                 rc = llc_ui_autobind(sock, addr);
>  909                 if (rc)
>  910                         goto release;
>  911         }
>  912         hdrlen = llc->dev->hard_header_len + llc_ui_header_len(sk, addr);
> 
> looks like llc->dev was null, (understandable, given Trinity doesn't really know
> how to set up llc beyond random socket()/setsockopt() calls).
> 
> llc_ui_autobind returns -ENODEV in that case, so it looks like the SOCK_ZAPPED test
> was false. Something like the patch below maybe ? It feels ugly to be duplicating that
> test there, but if this is agreed upon I'll resubmit this properly.

I figured it's something more complicated than that since trinity stumbled on it only
now and I don't see any code changes in that area. I'll test it with the patch.


Thanks,
Sasha
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