[PATCH v2 1/2] media: az6007: fix out-of-bounds in az6007_i2c_xfer()

[Jeongjun Park <aha310510@gmail.com>]

Because the blen is not properly bounds-checked in __az6007_read/write,
it is easy to get out-of-bounds errors in az6007_i2c_xfer later.

Therefore, we need to add bounds-checking to __az6007_read/write to
resolve this.

Cc: <stable@vger.kernel.org>
Reported-by: syzbot+0192952caa411a3be209@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=0192952caa411a3be209
Fixes: 786baecfe78f ("[media] dvb-usb: move it to drivers/media/usb/dvb-usb")
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
---
v2: Change to fix the root cause of oob
- Link to v1: https://lore.kernel.org/all/20250421105555.34984-1-aha310510@gmail.com/
---
 drivers/media/usb/dvb-usb-v2/az6007.c | 62 +++++++++++++++------------
 1 file changed, 34 insertions(+), 28 deletions(-)

diff --git a/drivers/media/usb/dvb-usb-v2/az6007.c b/drivers/media/usb/dvb-usb-v2/az6007.c
index 65ef045b74ca..4202042bdb55 100644
--- a/drivers/media/usb/dvb-usb-v2/az6007.c
+++ b/drivers/media/usb/dvb-usb-v2/az6007.c
@@ -97,11 +97,17 @@ static struct mt2063_config az6007_mt2063_config = {
 	.refclock = 36125000,
 };
 
-static int __az6007_read(struct usb_device *udev, u8 req, u16 value,
-			    u16 index, u8 *b, int blen)
+static int __az6007_read(struct usb_device *udev, struct az6007_device_state *st,
+			    u8 req, u16 value, u16 index, u8 *b, int blen)
 {
 	int ret;
 
+	if (blen > sizeof(st->data)) {
+		pr_err("az6007: tried to read %d bytes, but I2C max size is %lu bytes\n",
+		       blen, sizeof(st->data));
+		return -EOPNOTSUPP;
+	}
+
 	ret = usb_control_msg(udev,
 			      usb_rcvctrlpipe(udev, 0),
 			      req,
@@ -125,24 +131,30 @@ static int __az6007_read(struct usb_device *udev, u8 req, u16 value,
 static int az6007_read(struct dvb_usb_device *d, u8 req, u16 value,
 			    u16 index, u8 *b, int blen)
 {
-	struct az6007_device_state *st = d->priv;
+	struct az6007_device_state *st = d_to_priv(d);
 	int ret;
 
 	if (mutex_lock_interruptible(&st->mutex) < 0)
 		return -EAGAIN;
 
-	ret = __az6007_read(d->udev, req, value, index, b, blen);
+	ret = __az6007_read(d->udev, st, req, value, index, b, blen);
 
 	mutex_unlock(&st->mutex);
 
 	return ret;
 }
 
-static int __az6007_write(struct usb_device *udev, u8 req, u16 value,
-			     u16 index, u8 *b, int blen)
+static int __az6007_write(struct usb_device *udev, struct az6007_device_state *st,
+			    u8 req, u16 value, u16 index, u8 *b, int blen)
 {
 	int ret;
 
+	if (blen > sizeof(st->data)) {
+		pr_err("az6007: tried to write %d bytes, but I2C max size is %lu bytes\n",
+		       blen, sizeof(st->data));
+		return -EOPNOTSUPP;
+	}
+
 	if (az6007_xfer_debug) {
 		printk(KERN_DEBUG "az6007: OUT req: %02x, value: %04x, index: %04x\n",
 		       req, value, index);
@@ -150,12 +162,6 @@ static int __az6007_write(struct usb_device *udev, u8 req, u16 value,
 				     DUMP_PREFIX_NONE, b, blen);
 	}
 
-	if (blen > 64) {
-		pr_err("az6007: tried to write %d bytes, but I2C max size is 64 bytes\n",
-		       blen);
-		return -EOPNOTSUPP;
-	}
-
 	ret = usb_control_msg(udev,
 			      usb_sndctrlpipe(udev, 0),
 			      req,
@@ -172,13 +178,13 @@ static int __az6007_write(struct usb_device *udev, u8 req, u16 value,
 static int az6007_write(struct dvb_usb_device *d, u8 req, u16 value,
 			    u16 index, u8 *b, int blen)
 {
-	struct az6007_device_state *st = d->priv;
+	struct az6007_device_state *st = d_to_priv(d);
 	int ret;
 
 	if (mutex_lock_interruptible(&st->mutex) < 0)
 		return -EAGAIN;
 
-	ret = __az6007_write(d->udev, req, value, index, b, blen);
+	ret = __az6007_write(d->udev, st, req, value, index, b, blen);
 
 	mutex_unlock(&st->mutex);
 
@@ -775,7 +781,7 @@ static int az6007_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 			value = addr | (1 << 8);
 			length = 6 + msgs[i + 1].len;
 			len = msgs[i + 1].len;
-			ret = __az6007_read(d->udev, req, value, index,
+			ret = __az6007_read(d->udev, st, req, value, index,
 					    st->data, length);
 			if (ret >= len) {
 				for (j = 0; j < len; j++)
@@ -788,7 +794,7 @@ static int az6007_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 			if (az6007_xfer_debug)
 				printk(KERN_DEBUG "az6007: I2C W addr=0x%x len=%d\n",
 				       addr, msgs[i].len);
-			if (msgs[i].len < 1) {
+			if (msgs[i].len < 1 && msgs[i].len > 64) {
 				ret = -EIO;
 				goto err;
 			}
@@ -796,11 +802,8 @@ static int az6007_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 			index = msgs[i].buf[0];
 			value = addr | (1 << 8);
 			length = msgs[i].len - 1;
-			len = msgs[i].len - 1;
-			for (j = 0; j < len; j++)
-				st->data[j] = msgs[i].buf[j + 1];
-			ret =  __az6007_write(d->udev, req, value, index,
-					      st->data, length);
+			ret =  __az6007_write(d->udev, st, req, value, index,
+					      &msgs[i].buf[1], length);
 		} else {
 			/* read bytes */
 			if (az6007_xfer_debug)
@@ -815,10 +818,12 @@ static int az6007_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 			value = addr;
 			length = msgs[i].len + 6;
 			len = msgs[i].len;
-			ret = __az6007_read(d->udev, req, value, index,
+			ret = __az6007_read(d->udev, st, req, value, index,
 					    st->data, length);
-			for (j = 0; j < len; j++)
-				msgs[i].buf[j] = st->data[j + 5];
+			if (ret >= len) {
+				for (j = 0; j < len; j++)
+					msgs[i].buf[j] = st->data[j + 5];
+			}
 		}
 		if (ret < 0)
 			goto err;
@@ -845,6 +850,7 @@ static const struct i2c_algorithm az6007_i2c_algo = {
 
 static int az6007_identify_state(struct dvb_usb_device *d, const char **name)
 {
+	struct az6007_device_state *state = d_to_priv(d);
 	int ret;
 	u8 *mac;
 
@@ -855,7 +861,7 @@ static int az6007_identify_state(struct dvb_usb_device *d, const char **name)
 		return -ENOMEM;
 
 	/* Try to read the mac address */
-	ret = __az6007_read(d->udev, AZ6007_READ_DATA, 6, 0, mac, 6);
+	ret = __az6007_read(d->udev, state, AZ6007_READ_DATA, 6, 0, mac, 6);
 	if (ret == 6)
 		ret = WARM;
 	else
@@ -864,9 +870,9 @@ static int az6007_identify_state(struct dvb_usb_device *d, const char **name)
 	kfree(mac);
 
 	if (ret == COLD) {
-		__az6007_write(d->udev, 0x09, 1, 0, NULL, 0);
-		__az6007_write(d->udev, 0x00, 0, 0, NULL, 0);
-		__az6007_write(d->udev, 0x00, 0, 0, NULL, 0);
+		__az6007_write(d->udev, state, 0x09, 1, 0, NULL, 0);
+		__az6007_write(d->udev, state, 0x00, 0, 0, NULL, 0);
+		__az6007_write(d->udev, state, 0x00, 0, 0, NULL, 0);
 	}
 
 	pr_debug("Device is on %s state\n",
--