Subject: Re: [PATCH AUTOSEL 5.7 264/274] vxlan: Avoid infinite loop when suppressing NS messages with invalid options

From: Ido Schimmel <[email-masked]>
Date: Tue, 9 Jun 2020 09:55:48 +0300

On Mon, Jun 08, 2020 at 07:05:57PM -0400, Sasha Levin wrote:
> From: Ido Schimmel <[email-masked]>
> 
> [ Upstream commit 8066e6b449e050675df48e7c4b16c29f00507ff0 ]

Hi,

In the same patch set I also included a similar fix for the bridge
module:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=53fc685243bd6fb90d90305cea54598b78d3cbfc

But I don't see it in the patch sets you sent.

Don't see it here as well:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git/tree/queue-5.7
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/log/?h=linux-5.7.y

Did it get lost or it's just pending somewhere else?

Thanks

> 
> When proxy mode is enabled the vxlan device might reply to Neighbor
> Solicitation (NS) messages on behalf of remote hosts.
> 
> In case the NS message includes the "Source link-layer address" option
> [1], the vxlan device will use the specified address as the link-layer
> destination address in its reply.
> 
> To avoid an infinite loop, break out of the options parsing loop when
> encountering an option with length zero and disregard the NS message.
> 
> This is consistent with the IPv6 ndisc code and RFC 4886 which states
> that "Nodes MUST silently discard an ND packet that contains an option
> with length zero" [2].
> 
> [1] https://tools.ietf.org/html/rfc4861#section-4.3
> [2] https://tools.ietf.org/html/rfc4861#section-4.6
> 
> Fixes: 4b29dba9c085 ("vxlan: fix nonfunctional neigh_reduce()")
> Signed-off-by: Ido Schimmel <[email-masked]>
> Acked-by: Nikolay Aleksandrov <[email-masked]>
> Signed-off-by: David S. Miller <[email-masked]>
> Signed-off-by: Sasha Levin <[email-masked]>
> ---
>  drivers/net/vxlan.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
> index a5b415fed11e..779e56c43d27 100644
> --- a/drivers/net/vxlan.c
> +++ b/drivers/net/vxlan.c
> @@ -1924,6 +1924,10 @@ static struct sk_buff *vxlan_na_create(struct sk_buff *request,
>  	ns_olen = request->len - skb_network_offset(request) -
>  		sizeof(struct ipv6hdr) - sizeof(*ns);
>  	for (i = 0; i < ns_olen-1; i += (ns->opt[i+1]<<3)) {
> +		if (!ns->opt[i + 1]) {
> +			kfree_skb(reply);
> +			return NULL;
> +		}
>  		if (ns->opt[i] == ND_OPT_SOURCE_LL_ADDR) {
>  			daddr = ns->opt + i + sizeof(struct nd_opt_hdr);
>  			break;
> -- 
> 2.25.1
>