From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Sun, 5 Jul 2020 21:49:15 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c0d3.blue; s=2018; t=1593978556; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=nKHluXxwUVzurMKE6PUs6fbpMqBoqqTeZ7p5ILBCNf0=; b=nLmzWjczwQSgfZJJDP856kNnRZO0Dg5HeFABdFqkVbnIv2qTovOJEIsv2+aMQW4t+AVtBC P7LatRyPUuuTZrzJCbIxKsVEYrpl5qkQA849wBGxqO7Ib79joFGqJQtvPK5mAgmY3/NDo7 VrhHn2XvixQ6zxwpGSv8EAOkpQa82ETkxTleK9tv9zImAp1m48rWREXy3i9ECssE7WRGea G/v2lrL4BkSYcrGzqnEPOPQrOAZERqMuehaKgPgwBIbHE63rtK/FINX0oXw/N/EaXzkkEr 1ixqhgJoos1Ag5wdmuMzmtvbBYfKZH7XVufaE/wqIs6gP5xSp7USewr/jRCfMA== From: Linus =?utf-8?Q?L=C3=BCssing?= Message-ID: <20200705194915.GD2648@otheros> References: <20200705182234.10257-1-linus.luessing@c0d3.blue> <093beb97-87e8-e112-78ad-b3e4fe230cdb@cumulusnetworks.com> <20200705190851.GC2648@otheros> <4728ef5e-0036-7de6-8b6f-f29885d76473@cumulusnetworks.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4728ef5e-0036-7de6-8b6f-f29885d76473@cumulusnetworks.com> Subject: Re: [Bridge] [PATCH net] bridge: mcast: Fix MLD2 Report IPv6 payload length check List-Id: Linux Ethernet Bridging List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Nikolay Aleksandrov Cc: Martin Weinelt , netdev@vger.kernel.org, Roopa Prabhu , bridge@lists.linux-foundation.org, linux-kernel@vger.kernel.org, "David S . Miller" On Sun, Jul 05, 2020 at 10:11:39PM +0300, Nikolay Aleksandrov wrote: > On 7/5/20 10:08 PM, Linus Lüssing wrote: > > On Sun, Jul 05, 2020 at 09:33:13PM +0300, Nikolay Aleksandrov wrote: > > > On 05/07/2020 21:22, Linus Lüssing wrote: > > > > Commit e57f61858b7c ("net: bridge: mcast: fix stale nsrcs pointer in > > > > igmp3/mld2 report handling") introduced a small bug which would potentially > > > > lead to accepting an MLD2 Report with a broken IPv6 header payload length > > > > field. > > > > > > > > The check needs to take into account the 2 bytes for the "Number of > > > > Sources" field in the "Multicast Address Record" before reading it. > > > > And not the size of a pointer to this field. > > > > > > > > Fixes: e57f61858b7c ("net: bridge: mcast: fix stale nsrcs pointer in igmp3/mld2 report handling") > > > > Signed-off-by: Linus Lüssing > > > > --- > > > > net/bridge/br_multicast.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > > > I'd rather be more concerned with it rejecting a valid report due to wrong size. The ptr > > > size would always be bigger. :) > > > > > > Thanks! > > > Acked-by: Nikolay Aleksandrov > > > > Aiy, you're right, it's the other way round. I'll update the > > commit message and send a v2 in a minute, with your Acked-by > > included. > > > > By the way, I can't verify at the moment, but I think we can drop that whole > hunk altogether since skb_header_pointer() is used and it will simply return > an error if there isn't enough data for nsrcs. > Hm, while unlikely, the IPv6 packet / header payload length might be shorter than the frame / skb size. And even though it wouldn't crash reading over the IPv6 packet length, especially as skb_header_pointer() is used, I think we should still avoid reading over the size indicated by the IPv6 header payload length field, to stay protocol compliant. Does that make sense?