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: 11eeef4 ("netfilter: passive OS fingerprint xtables match") Signed-off-by: Pablo Neira Ayuso <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
akeromi · May 22, 2021 · e11924b · e11924b
1 parent bb101fb
commit e11924b
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/net/netfilter/nfnetlink_osf.c b/net/netfilter/nfnetlink_osf.c
@@ -191,6 +191,8 @@ 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;