From cb6657bde2a5a34bc05461e680a1ee19e82b0353 Mon Sep 17 00:00:00 2001 From: Paul Chaignon Date: Fri, 1 Aug 2025 11:48:15 +0200 Subject: [PATCH] bpf: Check netfilter ctx accesses are aligned [ Upstream commit 9e6448f7b1efb27f8d508b067ecd33ed664a4246 ] Similarly to the previous patch fixing the flow_dissector ctx accesses, nf_is_valid_access also doesn't check that ctx accesses are aligned. Contrary to flow_dissector programs, netfilter programs don't have context conversion. The unaligned ctx accesses are therefore allowed by the verifier. Fixes: fd9c663b9ad6 ("bpf: minimal support for programs hooked into netfilter framework") Signed-off-by: Paul Chaignon Acked-by: Yonghong Song Acked-by: Eduard Zingerman Link: https://lore.kernel.org/r/853ae9ed5edaa5196e8472ff0f1bb1cc24059214.1754039605.git.paul.chaignon@gmail.com Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- net/netfilter/nf_bpf_link.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/netfilter/nf_bpf_link.c b/net/netfilter/nf_bpf_link.c index 25bbac8986c22..c12250e50a8b2 100644 --- a/net/netfilter/nf_bpf_link.c +++ b/net/netfilter/nf_bpf_link.c @@ -295,6 +295,9 @@ static bool nf_is_valid_access(int off, int size, enum bpf_access_type type, if (off < 0 || off >= sizeof(struct bpf_nf_ctx)) return false; + if (off % size != 0) + return false; + if (type == BPF_WRITE) return false; -- 2.47.3