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netfilter: nfnetlink_osf: Fix a missing skb_header_pointer() NULL check

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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: 11eeef41d5 ("netfilter: passive OS fingerprint xtables match")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso 2021-05-05 22:25:24 +02:00
parent 7072a355ba
commit 5e024c3254
1 changed files with 2 additions and 0 deletions
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2
net/netfilter/nfnetlink_osf.c
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@ -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;