From 837f21aacf5a714c23ddaadbbc5212f9b661e3f7 Mon Sep 17 00:00:00 2001 From: Prasad J Pandit Date: Fri, 20 Nov 2015 11:50:31 +0530 Subject: net: pcnet: add check to validate receive data size(CVE-2015-7504) 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 Reviewed-by: Michael S. Tsirkin 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; } -- cgit v1.1