From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarek Poplawski Subject: [PATCH][AX25] ax25_out: check skb for NULL in ax25_kick() Date: Wed, 13 Feb 2008 11:56:07 +0000 Message-ID: <20080213115607.GB2867@ff.dom.local> References: <20080206074529.GC4496@ff.dom.local> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jann Traschewski , Bernard Pidoux F6BVP , Ralf Baechle , netdev@vger.kernel.org To: David Miller Return-path: Received: from fk-out-0910.google.com ([209.85.128.189]:61589 "EHLO fk-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755134AbYBMLtA (ORCPT ); Wed, 13 Feb 2008 06:49:00 -0500 Received: by fk-out-0910.google.com with SMTP id z23so5292794fkz.5 for ; Wed, 13 Feb 2008 03:48:55 -0800 (PST) Content-Disposition: inline In-Reply-To: <20080206074529.GC4496@ff.dom.local> Sender: netdev-owner@vger.kernel.org List-ID: Hi, Here is an "official" version of "testing patch #2" from this thread. The only difference: ax25->vs is changed only after checking skb is not NULL (plus a comment). IMHO it could be applied. Thanks, Jarek P. ----------------> Subject: [AX25] ax25_out: check skb for NULL in ax25_kick() According to some OOPS reports ax25_kick tries to clone NULL skbs sometimes. It looks like a race with ax25_clear_queues(). Probably there is no need to add more than a simple check for this yet. Another report suggested there are probably also cases where ax25 ->paclen == 0 can happen in ax25_output(); this wasn't confirmed during testing but let's leave this debugging check for some time. Reported-and-tested-by: Jann Traschewski Signed-off-by: Jarek Poplawski --- diff -Nurp 2.6.24-mm1-/net/ax25/ax25_out.c 2.6.24-mm1+/net/ax25/ax25_out.c --- 2.6.24-mm1-/net/ax25/ax25_out.c 2008-01-24 22:58:37.000000000 +0000 +++ 2.6.24-mm1+/net/ax25/ax25_out.c 2008-02-13 10:43:50.000000000 +0000 @@ -117,6 +117,12 @@ void ax25_output(ax25_cb *ax25, int pacl unsigned char *p; int frontlen, len, fragno, ka9qfrag, first = 1; + if (paclen < 16) { + WARN_ON_ONCE(1); + kfree_skb(skb); + return; + } + if ((skb->len - 1) > paclen) { if (*skb->data == AX25_P_TEXT) { skb_pull(skb, 1); /* skip PID */ @@ -251,8 +257,6 @@ void ax25_kick(ax25_cb *ax25) if (start == end) return; - ax25->vs = start; - /* * Transmit data until either we're out of data to send or * the window is full. Send a poll on the final I frame if @@ -261,8 +265,13 @@ void ax25_kick(ax25_cb *ax25) /* * Dequeue the frame and copy it. + * Check for race with ax25_clear_queues(). */ skb = skb_dequeue(&ax25->write_queue); + if (!skb) + return; + + ax25->vs = start; do { if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {