From d00615dc5053d7a8737c73cf6a3a3b1b8846ffae Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Thu, 16 Feb 2023 16:41:48 -0800 Subject: bpf: bpf_fib_lookup should not return neigh in NUD_FAILED state commit 1fe4850b34ab512ff911e2c035c75fb6438f7307 upstream. The bpf_fib_lookup() helper does not only look up the fib (ie. route) but it also looks up the neigh. Before returning the neigh, the helper does not check for NUD_VALID. When a neigh state (neigh->nud_state) is in NUD_FAILED, its dmac (neigh->ha) could be all zeros. The helper still returns SUCCESS instead of NO_NEIGH in this case. Because of the SUCCESS return value, the bpf prog directly uses the returned dmac and ends up filling all zero in the eth header. This patch checks for NUD_VALID and returns NO_NEIGH if the neigh is not valid. Signed-off-by: Martin KaFai Lau Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20230217004150.2980689-3-martin.lau@linux.dev Signed-off-by: Greg Kroah-Hartman --- net/core/filter.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index 43cc1fe58a2c..a00a4b5476d4 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5816,7 +5816,7 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params, neigh = __ipv6_neigh_lookup_noref_stub(dev, dst); } - if (!neigh) + if (!neigh || !(neigh->nud_state & NUD_VALID)) return BPF_FIB_LKUP_RET_NO_NEIGH; return bpf_fib_set_fwd_params(params, neigh, dev, mtu); @@ -5931,7 +5931,7 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params, * not needed here. */ neigh = __ipv6_neigh_lookup_noref_stub(dev, dst); - if (!neigh) + if (!neigh || !(neigh->nud_state & NUD_VALID)) return BPF_FIB_LKUP_RET_NO_NEIGH; return bpf_fib_set_fwd_params(params, neigh, dev, mtu); -- cgit v1.2.3