V4L/DVB (9621): Avoid writing outside shadow.bytes[] array

There were no check about the limits of shadow.bytes array. This offers
a risk of writing values outside the limits, overriding other data
areas.

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

1 files changed, 27 insertions, 3 deletions

diff --git a/drivers/media/video/tvaudio.c b/drivers/media/video/tvaudio.c
index 5ec369d54e6e..55b39b9a33d9 100644
--- a/drivers/media/video/tvaudio.c
+++ b/drivers/media/video/tvaudio.c
@@ -154,7 +154,7 @@ static int chip_write(struct CHIPSTATE *chip, int subaddr, int val)
 {
         unsigned char buffer[2];
 
-        if (-1 == subaddr) {
+        if (subaddr < 0) {
                 v4l_dbg(1, debug, chip->c, "%s: chip_write: 0x%x\n",
                         chip->c->name, val);
                 chip->shadow.bytes[1] = val;
@@ -165,6 +165,13 @@ static int chip_write(struct CHIPSTATE *chip, int subaddr, int val)
                         return -1;
                 }
         } else {
+                if (subaddr + 1 >= ARRAY_SIZE(chip->shadow.bytes)) {
+                        v4l_info(chip->c,
+                                "Tried to access a non-existent register: %d\n",
+                                subaddr);
+                        return -EINVAL;
+                }
+
                 v4l_dbg(1, debug, chip->c, "%s: chip_write: reg%d=0x%x\n",
                         chip->c->name, subaddr, val);
                 chip->shadow.bytes[subaddr+1] = val;
@@ -179,12 +186,20 @@ static int chip_write(struct CHIPSTATE *chip, int subaddr, int val)
         return 0;
 }
 
-static int chip_write_masked(struct CHIPSTATE *chip, int subaddr, int val, int mask)
+static int chip_write_masked(struct CHIPSTATE *chip,
+                             int subaddr, int val, int mask)
 {
         if (mask != 0) {
-                if (-1 == subaddr) {
+                if (subaddr < 0) {
                         val = (chip->shadow.bytes[1] & ~mask) | (val & mask);
                 } else {
+                        if (subaddr + 1 >= ARRAY_SIZE(chip->shadow.bytes)) {
+                                v4l_info(chip->c,
+                                        "Tried to access a non-existent register: %d\n",
+                                        subaddr);
+                                return -EINVAL;
+                        }
+
                         val = (chip->shadow.bytes[subaddr+1] & ~mask) | (val & mask);
                 }
         }
@@ -230,6 +245,15 @@ static int chip_cmd(struct CHIPSTATE *chip, char *name, audiocmd *cmd)
         if (0 == cmd->count)
                 return 0;
 
+        if (cmd->count + cmd->bytes[0] - 1 >= ARRAY_SIZE(chip->shadow.bytes)) {
+                v4l_info(chip->c,
+                         "Tried to access a non-existent register range: %d to %d\n",
+                         cmd->bytes[0] + 1, cmd->bytes[0] + cmd->count - 1);
+                return -EINVAL;
+        }
+
+        /* FIXME: it seems that the shadow bytes are wrong bellow !*/
+
         /* update our shadow register set; print bytes if (debug > 0) */
         v4l_dbg(1, debug, chip->c, "%s: chip_cmd(%s): reg=%d, data:",
                 chip->c->name, name,cmd->bytes[0]);