Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934591AbcLMTzA (ORCPT ); Tue, 13 Dec 2016 14:55:00 -0500 Received: from mx2.suse.de ([195.135.220.15]:54211 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934322AbcLMTxW (ORCPT ); Tue, 13 Dec 2016 14:53:22 -0500 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Eric Dumazet , "David S . Miller" , Jiri Slaby Subject: [PATCH 3.12 32/38] net/dccp: fix use-after-free in dccp_invalid_packet Date: Tue, 13 Dec 2016 20:52:58 +0100 Message-Id: <7d4c3e3e3d69e854333e664a3e6071a8da65e879.1481658746.git.jslaby@suse.cz> X-Mailer: git-send-email 2.11.0 In-Reply-To: <15034b96ec06ee859b67c6cd4e3be569a4ef286b.1481658746.git.jslaby@suse.cz> References: <15034b96ec06ee859b67c6cd4e3be569a4ef286b.1481658746.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1914 Lines: 60 From: Eric Dumazet 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 Reported-by: Andrey Konovalov Signed-off-by: David S. Miller Signed-off-by: Jiri Slaby --- 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