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: 11eeef41d5
("netfilter: passive OS fingerprint xtables match")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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@ -186,6 +186,8 @@ static const struct tcphdr *nf_osf_hdr_ctx_init(struct nf_osf_hdr_ctx *ctx,
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ctx->optp = skb_header_pointer(skb, ip_hdrlen(skb) +
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ctx->optp = skb_header_pointer(skb, ip_hdrlen(skb) +
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sizeof(struct tcphdr), ctx->optsize, opts);
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sizeof(struct tcphdr), ctx->optsize, opts);
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if (!ctx->optp)
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return NULL;
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}
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}
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return tcp;
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return tcp;
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