[media] firewire: firedtv-avc: fix more potential buffer overflow

"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().

[mchehab@osg.samsung.com: as I merged the version 1 of the patch, I needed
 to rebase to apply just the differences between v1 and v2]
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/media/firewire/firedtv-avc.c b/drivers/media/firewire/firedtv-avc.c
index ac17567f0822..251a556112a9 100644
--- a/drivers/media/firewire/firedtv-avc.c
+++ b/drivers/media/firewire/firedtv-avc.c
@@ -1157,7 +1157,7 @@ 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) - write_pos) {
+                if (program_info_length > sizeof(c->operand) - 4 - write_pos) {
                         ret = -EINVAL;
                         goto out;
                 }
@@ -1184,7 +1184,8 @@ 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) - write_pos) {
+                        if (es_info_length > sizeof(c->operand) - 4 -
+                                             write_pos) {
                                 ret = -EINVAL;
                                 goto out;
                         }