[media] si2168: Bounds check firmware

When reading the firmware and sending commands, the length must
be bounds checked to avoid overrunning the size of the command
buffer and smashing the stack if the firmware is not in the expected
format:

si2168 11-0064: found a 'Silicon Labs Si2168-B40'
si2168 11-0064: downloading firmware from file 'dvb-demod-si2168-b40-01.fw'
si2168 11-0064: firmware download failed -95
Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffffa085708f

Add the proper check.

Cc: stable@kernel.org
Reported-by: Stuart Auchterlonie <sauchter@redhat.com>
Reviewed-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Laura Abbott <labbott@fedoraproject.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

diff --git a/drivers/media/dvb-frontends/si2168.c b/drivers/media/dvb-frontends/si2168.c
index 81788c5a44d838dc1f6e27e7c060db174af56913..821a8f481507a14ec3857c66cd7c4744a6ac3efd 100644 (file)
--- a/drivers/media/dvb-frontends/si2168.c
+++ b/drivers/media/dvb-frontends/si2168.c
@@ -502,6 +502,10 @@ static int si2168_init(struct dvb_frontend *fe)
                /* firmware is in the new format */
                for (remaining = fw->size; remaining > 0; remaining -= 17) {
                        len = fw->data[fw->size - remaining];
+                       if (len > SI2168_ARGLEN) {
+                               ret = -EINVAL;
+                               break;
+                       }
                        memcpy(cmd.args, &fw->data[(fw->size - remaining) + 1], len);
                        cmd.wlen = len;
                        cmd.rlen = 1;