[PATCH 5.19 273/717] netfilter: nft_fib: Fix for rpath check with VRF devices

Greg Kroah-Hartman
2022-10-22T08:00:38Z

From: Phil Sutter <phil@nwl.cc>

[ Upstream commit 2a8a7c0eaa8747c16aa4a48d573aa920d5c00a5c ]

Analogous to commit b575b24b8eee3 ("netfilter: Fix rpfilter
dropping vrf packets by mistake") but for nftables fib expression:
Add special treatment of VRF devices so that typical reverse path
filtering via 'fib saddr . iif oif' expression works as expected.

Fixes: f6d0cbcf09c50 ("netfilter: nf_tables: add fib expression")
Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/netfilter/nft_fib_ipv4.c | 3 +++
net/ipv6/netfilter/nft_fib_ipv6.c | 6 +++++-
2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/netfilter/nft_fib_ipv4.c b/net/ipv4/netfilter/nft_fib_ipv4.c
index b75cac69bd7e..7ade04ff972d 100644
--- a/net/ipv4/netfilter/nft_fib_ipv4.c
+++ b/net/ipv4/netfilter/nft_fib_ipv4.c
@@ -83,6 +83,9 @@ void nft_fib4_eval(const struct nft_expr *expr, struct nft_regs *regs,
else
oif = NULL;

+ if (priv->flags & NFTA_FIB_F_IIF)
+ fl4.flowi4_oif = l3mdev_master_ifindex_rcu(oif);
+
if (nft_hook(pkt) == NF_INET_PRE_ROUTING &&
nft_fib_is_loopback(pkt->skb, nft_in(pkt))) {
nft_fib_store_result(dest, priv, nft_in(pkt));
diff --git a/net/ipv6/netfilter/nft_fib_ipv6.c b/net/ipv6/netfilter/nft_fib_ipv6.c
index 8970d0b4faeb..1d7e520d9966 100644
--- a/net/ipv6/netfilter/nft_fib_ipv6.c
+++ b/net/ipv6/netfilter/nft_fib_ipv6.c
@@ -41,6 +41,9 @@ static int nft_fib6_flowi_init(struct flowi6 *fl6, const struct nft_fib *priv,
if (ipv6_addr_type(&fl6->daddr) & IPV6_ADDR_LINKLOCAL) {
lookup_flags |= RT6_LOOKUP_F_IFACE;
fl6->flowi6_oif = get_ifindex(dev ? dev : pkt->skb->dev);
+ } else if ((priv->flags & NFTA_FIB_F_IIF) &&
+ (netif_is_l3_master(dev) || netif_is_l3_slave(dev))) {
+ fl6->flowi6_oif = dev->ifindex;
}

if (ipv6_addr_type(&fl6->saddr) & IPV6_ADDR_UNICAST)
@@ -197,7 +200,8 @@ void nft_fib6_eval(const struct nft_expr *expr, struct nft_regs *regs,
if (rt->rt6i_flags & (RTF_REJECT | RTF_ANYCAST | RTF_LOCAL))
goto put_rt_err;

- if (oif && oif != rt->rt6i_idev->dev)
+ if (oif && oif != rt->rt6i_idev->dev &&
+ l3mdev_master_ifindex_rcu(rt->rt6i_idev->dev) != oif->ifindex)
goto put_rt_err;

nft_fib_store_result(dest, priv, rt->rt6i_idev->dev);
--
2.35.1