From c8e3c76cc8c526ab4f3ac52c9572d2e1bda231b0 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Wed, 5 May 2021 22:25:24 +0200 Subject: [PATCH] netfilter: nfnetlink_osf: Fix a missing skb_header_pointer() NULL check [ Upstream commit 5e024c325406470d1165a09c6feaf8ec897936be ] Do not assume that the tcph->doff field is correct when parsing for TCP options, skb_header_pointer() might fail to fetch these bits. Fixes: 11eeef41d5f6 ("netfilter: passive OS fingerprint xtables match") Signed-off-by: Pablo Neira Ayuso Signed-off-by: Sasha Levin --- net/netfilter/nfnetlink_osf.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/netfilter/nfnetlink_osf.c b/net/netfilter/nfnetlink_osf.c index 916a3c7f9eaf..79fbf37291f3 100644 --- a/net/netfilter/nfnetlink_osf.c +++ b/net/netfilter/nfnetlink_osf.c @@ -186,6 +186,8 @@ static const struct tcphdr *nf_osf_hdr_ctx_init(struct nf_osf_hdr_ctx *ctx, ctx->optp = skb_header_pointer(skb, ip_hdrlen(skb) + sizeof(struct tcphdr), ctx->optsize, opts); + if (!ctx->optp) + return NULL; } return tcp;