CVE-2017-14497 (published 2017-09-15T18:29Z)

The tpacket_rcv function in net/packet/af_packet.c in the Linux kernel before 4.13 mishandles vnet headers, which might allow local users to cause a denial of service (buffer overflow, and disk and memory corruption) or possibly have unspecified other impact via crafted system calls.

Severity: HIGH
CVSS v2 base score: 7.2 (AV:L/AC:L/Au:N/C:C/I:C/A:C)
CVSS v3 base score: 7.8, HIGH (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)

Weakness information:
cwe_id: CWE-119
cwe_name: Improper Restriction of Operations within the Bounds of a Memory Buffer
description: The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.
extended_description: 
            Certain languages allow direct addressing of memory locations and do not automatically ensure that these locations are valid for the memory buffer that is being referenced. This can cause read or write operations to be performed on memory locations that may be associated with other variables, data structures, or internal program data.
         
         

Fix information:
repo_url: https://github.com/torvalds/linux
commit_details: repo_url: https://github.com/torvalds/linux
author: Benjamin Poirier
author_date: 2017-08-28 14:29:41-04:00
msg: packet: Don't write vnet header beyond end of buffer

... which may happen with certain values of tp_reserve and maclen.

Fixes: 58d19b19cd99 ("packet: vnet_hdr support for tpacket_rcv")
Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
Cc: Willem de Bruijn <willemb@google.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
repository: repo_url: https://github.com/torvalds/linux
repo_name: torvalds/linux
description: Linux kernel source tree
repo_language: C
owner: torvalds
file_changes: filename: af_packet.c
change_type: ModificationType.MODIFY
diff: @@ -2191,6 +2191,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 	struct timespec ts;
 	__u32 ts_status;
 	bool is_drop_n_account = false;
+	bool do_vnet = false;
 
 	/* struct tpacket{2,3}_hdr is aligned to a multiple of TPACKET_ALIGNMENT.
 	 * We may add members to them until current aligned size without forcing
@@ -2241,8 +2242,10 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 		netoff = TPACKET_ALIGN(po->tp_hdrlen +
 				       (maclen < 16 ? 16 : maclen)) +
 				       po->tp_reserve;
-		if (po->has_vnet_hdr)
+		if (po->has_vnet_hdr) {
 			netoff += sizeof(struct virtio_net_hdr);
+			do_vnet = true;
+		}
 		macoff = netoff - maclen;
 	}
 	if (po->tp_version <= TPACKET_V2) {
@@ -2259,8 +2262,10 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 					skb_set_owner_r(copy_skb, sk);
 			}
 			snaplen = po->rx_ring.frame_size - macoff;
-			if ((int)snaplen < 0)
+			if ((int)snaplen < 0) {
 				snaplen = 0;
+				do_vnet = false;
+			}
 		}
 	} else if (unlikely(macoff + snaplen >
 			    GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len)) {
@@ -2273,6 +2278,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 		if (unlikely((int)snaplen < 0)) {
 			snaplen = 0;
 			macoff = GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len;
+			do_vnet = false;
 		}
 	}
 	spin_lock(&sk->sk_receive_queue.lock);
@@ -2298,7 +2304,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 	}
 	spin_unlock(&sk->sk_receive_queue.lock);
 
-	if (po->has_vnet_hdr) {
+	if (do_vnet) {
 		if (virtio_net_hdr_from_skb(skb, h.raw + macoff -
 					    sizeof(struct virtio_net_hdr),
 					    vio_le(), true)) {

programming_language: C