[PATCH] fix writing to unintended memory in pkt_generic_packet(); drivers/block/pktcdvd.c

[Roel Kluin <12o3l@tiscali.nl>]

CDROM_PACKET_SIZE is added as an offset to the pointer to unsigned char cmd[16].
The adjusted pointer is then used as a destination address in a call to
memset(). However, when CDROM_PACKET_SIZE is added to the pointer, it is
automatically scaled by the size of cmd, which is 16. This results in the call
to memset() writing to unintended memory.

Signed-off-by: Roel Kluin <12o3l@tiscali.nl>
---
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index a8130a4..548efcf 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -767,7 +767,7 @@ static int pkt_generic_packet(struct pktcdvd_device *pd, struct packet_command *
 	rq->cmd_len = COMMAND_SIZE(cgc->cmd[0]);
 	memcpy(rq->cmd, cgc->cmd, CDROM_PACKET_SIZE);
 	if (sizeof(rq->cmd) > CDROM_PACKET_SIZE)
-		memset(rq->cmd + CDROM_PACKET_SIZE, 0, sizeof(rq->cmd) - CDROM_PACKET_SIZE);
+		memset((char *)rq->cmd + CDROM_PACKET_SIZE, 0, sizeof(rq->cmd) - CDROM_PACKET_SIZE);
 
 	rq->timeout = 60*HZ;
 	rq->cmd_type = REQ_TYPE_BLOCK_PC;