[patch v2] [media] firewire: firedtv-avc: potential buffer overflow

[Dan Carpenter <dan.carpenter@oracle.com>]

"program_info_length" is user controlled and can go up to 4095.  The
operand[] array has 509 bytes so we need to add a limit here to prevent
buffer overflows.

The " - 4" in the limit check is because we have 4 bytes more data to
add after the memcpy().

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
v2:  The first version didn't have the - 4.  Thanks for catching that
Stafan.

diff --git a/drivers/media/firewire/firedtv-avc.c b/drivers/media/firewire/firedtv-avc.c
index d1a1a13..251a556 100644
--- a/drivers/media/firewire/firedtv-avc.c
+++ b/drivers/media/firewire/firedtv-avc.c
@@ -1157,6 +1157,10 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length)
 		if (pmt_cmd_id != 1 && pmt_cmd_id != 4)
 			dev_err(fdtv->device,
 				"invalid pmt_cmd_id %d\n", pmt_cmd_id);
+		if (program_info_length > sizeof(c->operand) - 4 - write_pos) {
+			ret = -EINVAL;
+			goto out;
+		}
 
 		memcpy(&c->operand[write_pos], &msg[read_pos],
 		       program_info_length);
@@ -1180,6 +1184,12 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length)
 				dev_err(fdtv->device, "invalid pmt_cmd_id %d "
 					"at stream level\n", pmt_cmd_id);
 
+			if (es_info_length > sizeof(c->operand) - 4 -
+					     write_pos) {
+				ret = -EINVAL;
+				goto out;
+			}
+
 			memcpy(&c->operand[write_pos], &msg[read_pos],
 			       es_info_length);
 			read_pos += es_info_length;