This is a note to let you know that I've just added the patch titled netfilter: ebtables: Fixes dropping of small packets in bridge nat to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: netfilter-ebtables-fixes-dropping-of-small-packets-i.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 399aab17023bb83776b53d6f70adbbac9de651ea Author: Timothée COCAULT <timothee.cocault@xxxxxxxxxx> Date: Wed Oct 14 12:36:15 2020 +0000 netfilter: ebtables: Fixes dropping of small packets in bridge nat [ Upstream commit 63137bc5882a1882c553d389fdeeeace86ee1741 ] Fixes an error causing small packets to get dropped. skb_ensure_writable expects the second parameter to be a length in the ethernet payload.=20 If we want to write the ethernet header (src, dst), we should pass 0. Otherwise, packets with small payloads (< ETH_ALEN) will get dropped. Fixes: c1a831167901 ("netfilter: bridge: convert skb_make_writable to skb_ensure_writable") Signed-off-by: Timothée COCAULT <timothee.cocault@xxxxxxxxxx> Reviewed-by: Florian Westphal <fw@xxxxxxxxx> Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/net/bridge/netfilter/ebt_dnat.c b/net/bridge/netfilter/ebt_dnat.c index 12a4f4d936810..3fda71a8579d1 100644 --- a/net/bridge/netfilter/ebt_dnat.c +++ b/net/bridge/netfilter/ebt_dnat.c @@ -21,7 +21,7 @@ ebt_dnat_tg(struct sk_buff *skb, const struct xt_action_param *par) { const struct ebt_nat_info *info = par->targinfo; - if (skb_ensure_writable(skb, ETH_ALEN)) + if (skb_ensure_writable(skb, 0)) return EBT_DROP; ether_addr_copy(eth_hdr(skb)->h_dest, info->mac); diff --git a/net/bridge/netfilter/ebt_redirect.c b/net/bridge/netfilter/ebt_redirect.c index 0cad62a4052b9..307790562b492 100644 --- a/net/bridge/netfilter/ebt_redirect.c +++ b/net/bridge/netfilter/ebt_redirect.c @@ -21,7 +21,7 @@ ebt_redirect_tg(struct sk_buff *skb, const struct xt_action_param *par) { const struct ebt_redirect_info *info = par->targinfo; - if (skb_ensure_writable(skb, ETH_ALEN)) + if (skb_ensure_writable(skb, 0)) return EBT_DROP; if (xt_hooknum(par) != NF_BR_BROUTING) diff --git a/net/bridge/netfilter/ebt_snat.c b/net/bridge/netfilter/ebt_snat.c index 27443bf229a3b..7dfbcdfc30e5d 100644 --- a/net/bridge/netfilter/ebt_snat.c +++ b/net/bridge/netfilter/ebt_snat.c @@ -22,7 +22,7 @@ ebt_snat_tg(struct sk_buff *skb, const struct xt_action_param *par) { const struct ebt_nat_info *info = par->targinfo; - if (skb_ensure_writable(skb, ETH_ALEN * 2)) + if (skb_ensure_writable(skb, 0)) return EBT_DROP; ether_addr_copy(eth_hdr(skb)->h_source, info->mac);