From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47005) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a3J3G-00064Y-Rz for qemu-devel@nongnu.org; Mon, 30 Nov 2015 02:39:11 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1a3J3C-0001zJ-B2 for qemu-devel@nongnu.org; Mon, 30 Nov 2015 02:39:10 -0500 From: Jason Wang Date: Mon, 30 Nov 2015 15:38:22 +0800 Message-Id: <1448869103-16281-1-git-send-email-jasowang@redhat.com> Subject: [Qemu-devel] [PATCH for 2.5 1/2] net: pcnet: add check to validate receive data size(CVE-2015-7504) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: jasowang@redhat.com, qemu-devel@nongnu.org Cc: Prasad J Pandit , qemu-stable@nongnu.org From: Prasad J Pandit In loopback mode, pcnet_receive routine appends CRC code to the receive buffer. If the data size given is same as the buffer size, the appended CRC code overwrites 4 bytes after s->buffer. Added a check to avoid that. Reported by: Qinghao Tang Cc: qemu-stable@nongnu.org Signed-off-by: Prasad J Pandit Signed-off-by: Jason Wang --- hw/net/pcnet.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/hw/net/pcnet.c b/hw/net/pcnet.c index 0eb3cc4..309c40b 100644 --- a/hw/net/pcnet.c +++ b/hw/net/pcnet.c @@ -1084,7 +1084,7 @@ ssize_t pcnet_receive(NetClientState *nc, const uint8_t *buf, size_t size_) uint32_t fcs = ~0; uint8_t *p = src; - while (p != &src[size-4]) + while (p != &src[size]) CRC(fcs, *p++); crc_err = (*(uint32_t *)p != htonl(fcs)); } @@ -1233,8 +1233,10 @@ static void pcnet_transmit(PCNetState *s) bcnt = 4096 - GET_FIELD(tmd.length, TMDL, BCNT); /* if multi-tmd packet outsizes s->buffer then skip it silently. - Note: this is not what real hw does */ - if (s->xmit_pos + bcnt > sizeof(s->buffer)) { + * Note: this is not what real hw does. + * Last four bytes of s->buffer are used to store CRC FCS code. + */ + if (s->xmit_pos + bcnt > sizeof(s->buffer) - 4) { s->xmit_pos = -1; goto txdone; } -- 2.5.0