From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Jones Subject: Re: net: llc: NULL ptr deref in llc_ui_sendmsg Date: Fri, 6 Jun 2014 11:42:31 -0400 Message-ID: <20140606154231.GA7629@redhat.com> References: <5391D971.4030001@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Arnaldo Carvalho de Melo , "David S. Miller" , "netdev@vger.kernel.org" , LKML To: Sasha Levin Return-path: Content-Disposition: inline In-Reply-To: <5391D971.4030001@oracle.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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. Dave diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c index 0080d2b0a8ae..9b192db9883b 100644 --- a/net/llc/af_llc.c +++ b/net/llc/af_llc.c @@ -908,6 +908,11 @@ static int llc_ui_sendmsg(struct kiocb *iocb, struct socket *sock, rc = llc_ui_autobind(sock, addr); if (rc) goto release; + } else { + if (!llc->dev) { + rc = -ENODEV; + goto release; + } } hdrlen = llc->dev->hard_header_len + llc_ui_header_len(sk, addr); size = hdrlen + len;