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Subject: Re: [PATCH 4.4 63/74] net: igmp: fix source address check for IGMPv3
 reports
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org
Cc:     stable@vger.kernel.org,
        Sebastian Gottschall <s.gottschall@dd-wrt.com>,
        Felix Fietkau <nbd@nbd.name>,
        "David S. Miller" <davem@davemloft.net>
References: <20180129123847.507563674@linuxfoundation.org>
 <20180129123850.383712554@linuxfoundation.org>
From:   Florian Wolters <florian@florian-wolters.de>
Message-ID: <cb899095-c5f7-ef8a-b595-d8db54f17d7d@florian-wolters.de>
Date:   Tue, 30 Jan 2018 14:22:55 +0100
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Tested-by: Florian Wolters <florian@florian-wolters.de>

I have tested this patch applied to 4.4.113 with positive result within
the fli4l project.


On 01/29/2018 01:57 PM, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Felix Fietkau <nbd@nbd.name>
> 
> 
> [ Upstream commit ad23b750933ea7bf962678972a286c78a8fa36aa ]
> 
> Commit "net: igmp: Use correct source address on IGMPv3 reports"
> introduced a check to validate the source address of locally generated
> IGMPv3 packets.
> Instead of checking the local interface address directly, it uses
> inet_ifa_match(fl4->saddr, ifa), which checks if the address is on the
> local subnet (or equal to the point-to-point address if used).
> 
> This breaks for point-to-point interfaces, so check against
> ifa->ifa_local directly.
> 
> Cc: Kevin Cernekee <cernekee@chromium.org>
> Fixes: a46182b00290 ("net: igmp: Use correct source address on IGMPv3 reports")
> Reported-by: Sebastian Gottschall <s.gottschall@dd-wrt.com>
> Signed-off-by: Felix Fietkau <nbd@nbd.name>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>  net/ipv4/igmp.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/net/ipv4/igmp.c
> +++ b/net/ipv4/igmp.c
> @@ -338,7 +338,7 @@ static __be32 igmpv3_get_srcaddr(struct
>  		return htonl(INADDR_ANY);
>  
>  	for_ifa(in_dev) {
> -		if (inet_ifa_match(fl4->saddr, ifa))
> +		if (fl4->saddr == ifa->ifa_local)
>  			return fl4->saddr;
>  	} endfor_ifa(in_dev);
>  
>