media: wl128x: prevent two potential buffer overflows

commit 9c2ccc324b3a6cbc865ab8b3e1a09e93d3c8ade9 upstream.

Smatch marks skb->data as untrusted so it warns that "evt_hdr->dlen"
can copy up to 255 bytes and we only have room for two bytes.  Even
if this comes from the firmware and we trust it, the new policy
generally is just to fix it as kernel hardenning.

I can't test this code so I tried to be very conservative.  I considered
not allowing "evt_hdr->dlen == 1" because it doesn't initialize the
whole variable but in the end I decided to allow it and manually
initialized "asic_id" and "asic_ver" to zero.

Fixes: e8454ff7b9a4 ("[media] drivers:media:radio: wl128x: FM Driver Common sources")
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+samsung@kernel.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/media/radio/wl128x/fmdrv_common.c b/drivers/media/radio/wl128x/fmdrv_common.c
index 2cd802281ccdde71c9ea524307a8c5438289c030..d2975a3f1d02ad8c7b67fedad8645def5976001b 100644 (file)
--- a/drivers/media/radio/wl128x/fmdrv_common.c
+++ b/drivers/media/radio/wl128x/fmdrv_common.c
@@ -494,7 +494,8 @@ int fmc_send_cmd(struct fmdev *fmdev, u8 fm_op, u16 type, void *payload,
                return -EIO;
        }
        /* Send response data to caller */
-       if (response != NULL && response_len != NULL && evt_hdr->dlen) {
+       if (response != NULL && response_len != NULL && evt_hdr->dlen &&
+           evt_hdr->dlen <= payload_len) {
                /* Skip header info and copy only response data */
                skb_pull(skb, sizeof(struct fm_event_msg_hdr));
                memcpy(response, skb->data, evt_hdr->dlen);
@@ -590,6 +591,8 @@ static void fm_irq_handle_flag_getcmd_resp(struct fmdev *fmdev)
                return;
 
        fm_evt_hdr = (void *)skb->data;
+       if (fm_evt_hdr->dlen > sizeof(fmdev->irq_info.flag))
+               return;
 
        /* Skip header info and copy only response data */
        skb_pull(skb, sizeof(struct fm_event_msg_hdr));
@@ -1318,7 +1321,8 @@ static int load_default_rx_configuration(struct fmdev *fmdev)
 /* Does FM power on sequence */
 static int fm_power_up(struct fmdev *fmdev, u8 mode)
 {
-       u16 payload, asic_id, asic_ver;
+       u16 payload;
+       __be16 asic_id = 0, asic_ver = 0;
        int resp_len, ret;
        u8 fw_name[50];