[PATCH 5.4 4/9] media: firewire: firedtv-avc: fix a buffer overflow in avc_ca_pmt()

Greg Kroah-Hartman
2021-11-04T14:16:51Z

From: Dan Carpenter <dan.carpenter@oracle.com>

commit 35d2969ea3c7d32aee78066b1f3cf61a0d935a4e upstream.

The bounds checking in avc_ca_pmt() is not strict enough. It should
be checking "read_pos + 4" because it's reading 5 bytes. If the
"es_info_length" is non-zero then it reads a 6th byte so there needs to
be an additional check for that.

I also added checks for the "write_pos". I don't think these are
required because "read_pos" and "write_pos" are tied together so
checking one ought to be enough. But they make the code easier to
understand for me. The check on write_pos is:

if (write_pos + 4 >= sizeof(c->operand) - 4) {

The first "+ 4" is because we're writing 5 bytes and the last " - 4"
is to leave space for the CRC.

The other problem is that "length" can be invalid. It comes from
"data_length" in fdtv_ca_pmt().

Cc: stable@vger.kernel.org
Reported-by: Luo Likang <luolikang@nsfocus.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/media/firewire/firedtv-avc.c | 14 +++++++++++---
drivers/media/firewire/firedtv-ci.c | 2 ++
2 files changed, 13 insertions(+), 3 deletions(-)

--- a/drivers/media/firewire/firedtv-avc.c
+++ b/drivers/media/firewire/firedtv-avc.c
@@ -1165,7 +1165,11 @@ int avc_ca_pmt(struct firedtv *fdtv, cha
read_pos += program_info_length;
write_pos += program_info_length;
}
- while (read_pos < length) {
+ while (read_pos + 4 < length) {
+ if (write_pos + 4 >= sizeof(c->operand) - 4) {
+ ret = -EINVAL;
+ goto out;
+ }
c->operand[write_pos++] = msg[read_pos++];
c->operand[write_pos++] = msg[read_pos++];
c->operand[write_pos++] = msg[read_pos++];
@@ -1177,13 +1181,17 @@ int avc_ca_pmt(struct firedtv *fdtv, cha
c->operand[write_pos++] = es_info_length >> 8;
c->operand[write_pos++] = es_info_length & 0xff;
if (es_info_length > 0) {
+ if (read_pos >= length) {
+ ret = -EINVAL;
+ goto out;
+ }
pmt_cmd_id = msg[read_pos++];
if (pmt_cmd_id != 1 && pmt_cmd_id != 4)
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) {
+ if (es_info_length > sizeof(c->operand) - 4 - write_pos ||
+ es_info_length > length - read_pos) {
ret = -EINVAL;
goto out;
}
--- a/drivers/media/firewire/firedtv-ci.c
+++ b/drivers/media/firewire/firedtv-ci.c
@@ -134,6 +134,8 @@ static int fdtv_ca_pmt(struct firedtv *f
} else {
data_length = msg->msg[3];
}
+ if (data_length > sizeof(msg->msg) - data_pos)
+ return -EINVAL;

return avc_ca_pmt(fdtv, &msg->msg[data_pos], data_length);
}