Commit 00b9bf63 authored by Eric Dumazet's avatar Eric Dumazet Committed by Ben Hutchings

net/dccp: fix use-after-free in dccp_invalid_packet

[ Upstream commit 648f0c28 ]

pskb_may_pull() can reallocate skb->head, we need to reload dh pointer
in dccp_invalid_packet() or risk use after free.

Bug found by Andrey Konovalov using syzkaller.
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reported-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
parent 03aeee0d
......@@ -730,6 +730,7 @@ int dccp_invalid_packet(struct sk_buff *skb)
{
const struct dccp_hdr *dh;
unsigned int cscov;
u8 dccph_doff;
if (skb->pkt_type != PACKET_HOST)
return 1;
......@@ -751,18 +752,19 @@ int dccp_invalid_packet(struct sk_buff *skb)
/*
* If P.Data Offset is too small for packet type, drop packet and return
*/
if (dh->dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
DCCP_WARN("P.Data Offset(%u) too small\n", dh->dccph_doff);
dccph_doff = dh->dccph_doff;
if (dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
DCCP_WARN("P.Data Offset(%u) too small\n", dccph_doff);
return 1;
}
/*
* If P.Data Offset is too too large for packet, drop packet and return
*/
if (!pskb_may_pull(skb, dh->dccph_doff * sizeof(u32))) {
DCCP_WARN("P.Data Offset(%u) too large\n", dh->dccph_doff);
if (!pskb_may_pull(skb, dccph_doff * sizeof(u32))) {
DCCP_WARN("P.Data Offset(%u) too large\n", dccph_doff);
return 1;
}
dh = dccp_hdr(skb);
/*
* If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
* has short sequence numbers), drop packet and return
......
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