[PATCH 3.12 32/38] net/dccp: fix use-after-free in dccp_invalid_packet
From: Jiri Slaby <hidden>
Date: 2016-12-13 19:55:00
Also in:
lkml
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Eric Dumazet <edumazet@google.com> 3.12-stable review patch. If anyone has any objections, please let me know. =============== [ Upstream commit 648f0c28df282636c0c8a7a19ca3ce5fc80a39c3 ] 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: Eric Dumazet <edumazet@google.com> Reported-by: Andrey Konovalov <redacted> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Jiri Slaby <redacted> --- net/dccp/ipv4.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 294c642fbebb..4332b7c25af0 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c@@ -742,6 +742,7 @@ 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;
@@ -763,18 +764,19 @@ 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
--
2.11.0