From 530aad77010b81526586dfc09130ec875cd084e4 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Wed, 5 Dec 2018 14:12:19 +0100 Subject: [PATCH] netfilter: seqadj: re-load tcp header pointer after possible head reallocation When adjusting sack block sequence numbers, skb_make_writable() gets called to make sure tcp options are all in the linear area, and buffer is not shared. This can cause tcp header pointer to get reallocated, so we must reaload it to avoid memory corruption. This bug pre-dates git history. Reported-by: Neel Mehta Reported-by: Shane Huntley Reported-by: Heather Adkins Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_conntrack_seqadj.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/net/netfilter/nf_conntrack_seqadj.c b/net/netfilter/nf_conntrack_seqadj.c index a975efd6b8c3..9da303461069 100644 --- a/net/netfilter/nf_conntrack_seqadj.c +++ b/net/netfilter/nf_conntrack_seqadj.c @@ -115,12 +115,12 @@ static void nf_ct_sack_block_adjust(struct sk_buff *skb, /* TCP SACK sequence number adjustment */ static unsigned int nf_ct_sack_adjust(struct sk_buff *skb, unsigned int protoff, - struct tcphdr *tcph, struct nf_conn *ct, enum ip_conntrack_info ctinfo) { - unsigned int dir, optoff, optend; + struct tcphdr *tcph = (void *)skb->data + protoff; struct nf_conn_seqadj *seqadj = nfct_seqadj(ct); + unsigned int dir, optoff, optend; optoff = protoff + sizeof(struct tcphdr); optend = protoff + tcph->doff * 4; @@ -128,6 +128,7 @@ static unsigned int nf_ct_sack_adjust(struct sk_buff *skb, if (!skb_make_writable(skb, optend)) return 0; + tcph = (void *)skb->data + protoff; dir = CTINFO2DIR(ctinfo); while (optoff < optend) { @@ -207,7 +208,7 @@ int nf_ct_seq_adjust(struct sk_buff *skb, ntohl(newack)); tcph->ack_seq = newack; - res = nf_ct_sack_adjust(skb, protoff, tcph, ct, ctinfo); + res = nf_ct_sack_adjust(skb, protoff, ct, ctinfo); out: spin_unlock_bh(&ct->lock);