[net,4/8] netfilter: nfnetlink_osf: Fix a missing skb_header_pointer() NULL check

Message ID 20210507174739.1850-5-pablo@netfilter.org
State New
Headers show
  • Netfilter fixes for net
Related show

Commit Message

Pablo Neira Ayuso May 7, 2021, 5:47 p.m.
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 <pablo@netfilter.org>
 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 e8f8875c6884..0fa2e2030427 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;