From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754553AbaCaARz (ORCPT ); Sun, 30 Mar 2014 20:17:55 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:36377 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753016AbaC3XZB (ORCPT ); Sun, 30 Mar 2014 19:25:01 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Jouni Malinen" , "Johannes Berg" Date: Mon, 31 Mar 2014 00:23:35 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 086/200] mac80211: fix fragmentation code, particularly for encryption In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.249 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.56-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Johannes Berg commit 338f977f4eb441e69bb9a46eaa0ac715c931a67f upstream. The "new" fragmentation code (since my rewrite almost 5 years ago) erroneously sets skb->len rather than using skb_trim() to adjust the length of the first fragment after copying out all the others. This leaves the skb tail pointer pointing to after where the data originally ended, and thus causes the encryption MIC to be written at that point, rather than where it belongs: immediately after the data. The impact of this is that if software encryption is done, then a) encryption doesn't work for the first fragment, the connection becomes unusable as the first fragment will never be properly verified at the receiver, the MIC is practically guaranteed to be wrong b) we leak up to 8 bytes of plaintext (!) of the packet out into the air This is only mitigated by the fact that many devices are capable of doing encryption in hardware, in which case this can't happen as the tail pointer is irrelevant in that case. Additionally, fragmentation is not used very frequently and would normally have to be configured manually. Fix this by using skb_trim() properly. Fixes: 2de8e0d999b8 ("mac80211: rewrite fragmentation") Reported-by: Jouni Malinen Signed-off-by: Johannes Berg [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- net/mac80211/tx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/mac80211/tx.c +++ b/net/mac80211/tx.c @@ -884,7 +884,7 @@ static int ieee80211_fragment(struct iee pos += fraglen; } - skb->len = hdrlen + per_fragm; + skb_trim(skb, hdrlen + per_fragm); return 0; }