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Date:   Mon, 14 Nov 2016 00:14:07 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Eyal Itkin" <eyal.itkin@...il.com>,
        "Stefan Richter" <stefanr@...6.in-berlin.de>
Subject: [PATCH 3.2 144/152] firewire: net: guard against rx buffer overflows

3.2.84-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Stefan Richter <stefanr@...6.in-berlin.de>

commit 667121ace9dbafb368618dbabcf07901c962ddac upstream.

The IP-over-1394 driver firewire-net lacked input validation when
handling incoming fragmented datagrams.  A maliciously formed fragment
with a respectively large datagram_offset would cause a memcpy past the
datagram buffer.

So, drop any packets carrying a fragment with offset + length larger
than datagram_size.

In addition, ensure that
  - GASP header, unfragmented encapsulation header, or fragment
    encapsulation header actually exists before we access it,
  - the encapsulated datagram or fragment is of nonzero size.

Reported-by: Eyal Itkin <eyal.itkin@...il.com>
Reviewed-by: Eyal Itkin <eyal.itkin@...il.com>
Fixes: CVE 2016-8633
Signed-off-by: Stefan Richter <stefanr@...6.in-berlin.de>
[bwh: Backported to 3.2: fwnet_receive_broadcast() never matches IPv6 packets]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/drivers/firewire/net.c
+++ b/drivers/firewire/net.c
@@ -677,6 +677,9 @@ static int fwnet_incoming_packet(struct
 	int retval;
 	u16 ether_type;
 
+	if (len <= RFC2374_UNFRAG_HDR_SIZE)
+		return 0;
+
 	hdr.w0 = be32_to_cpu(buf[0]);
 	lf = fwnet_get_hdr_lf(&hdr);
 	if (lf == RFC2374_HDR_UNFRAG) {
@@ -702,7 +705,12 @@ static int fwnet_incoming_packet(struct
 		return fwnet_finish_incoming_packet(net, skb, source_node_id,
 						    is_broadcast, ether_type);
 	}
+
 	/* A datagram fragment has been received, now the fun begins. */
+
+	if (len <= RFC2374_FRAG_HDR_SIZE)
+		return 0;
+
 	hdr.w1 = ntohl(buf[1]);
 	buf += 2;
 	len -= RFC2374_FRAG_HDR_SIZE;
@@ -716,6 +724,9 @@ static int fwnet_incoming_packet(struct
 	datagram_label = fwnet_get_hdr_dgl(&hdr);
 	dg_size = fwnet_get_hdr_dg_size(&hdr); /* ??? + 1 */
 
+	if (fg_off + len > dg_size)
+		return 0;
+
 	spin_lock_irqsave(&dev->lock, flags);
 
 	peer = fwnet_peer_find_by_node_id(dev, source_node_id, generation);
@@ -822,6 +833,22 @@ static void fwnet_receive_packet(struct
 	fw_send_response(card, r, rcode);
 }
 
+static int gasp_source_id(__be32 *p)
+{
+	return be32_to_cpu(p[0]) >> 16;
+}
+
+static u32 gasp_specifier_id(__be32 *p)
+{
+	return (be32_to_cpu(p[0]) & 0xffff) << 8 |
+	       (be32_to_cpu(p[1]) & 0xff000000) >> 24;
+}
+
+static u32 gasp_version(__be32 *p)
+{
+	return be32_to_cpu(p[1]) & 0xffffff;
+}
+
 static void fwnet_receive_broadcast(struct fw_iso_context *context,
 		u32 cycle, size_t header_length, void *header, void *data)
 {
@@ -832,9 +859,6 @@ static void fwnet_receive_broadcast(stru
 	__be32 *buf_ptr;
 	int retval;
 	u32 length;
-	u16 source_node_id;
-	u32 specifier_id;
-	u32 ver;
 	unsigned long offset;
 	unsigned long flags;
 
@@ -852,17 +876,13 @@ static void fwnet_receive_broadcast(stru
 
 	spin_unlock_irqrestore(&dev->lock, flags);
 
-	specifier_id =    (be32_to_cpu(buf_ptr[0]) & 0xffff) << 8
-			| (be32_to_cpu(buf_ptr[1]) & 0xff000000) >> 24;
-	ver = be32_to_cpu(buf_ptr[1]) & 0xffffff;
-	source_node_id = be32_to_cpu(buf_ptr[0]) >> 16;
-
-	if (specifier_id == IANA_SPECIFIER_ID && ver == RFC2734_SW_VERSION) {
-		buf_ptr += 2;
-		length -= IEEE1394_GASP_HDR_SIZE;
-		fwnet_incoming_packet(dev, buf_ptr, length, source_node_id,
+	if (length > IEEE1394_GASP_HDR_SIZE &&
+	    gasp_specifier_id(buf_ptr) == IANA_SPECIFIER_ID &&
+	    gasp_version(buf_ptr) == RFC2734_SW_VERSION)
+		fwnet_incoming_packet(dev, buf_ptr + 2,
+				      length - IEEE1394_GASP_HDR_SIZE,
+				      gasp_source_id(buf_ptr),
 				      context->card->generation, true);
-	}
 
 	packet.payload_length = dev->rcv_buffer_size;
 	packet.interrupt = 1;

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