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media: dvb-usb: digitv: fix null-ptr-deref in digitv_i2c_xfer()

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In digitv_i2c_xfer, msg is controlled by user. When msg[i].buf
is null and msg[i].len is zero, former checks on msg[i].buf would be
passed. Malicious data finally reach digitv_i2c_xfer. If accessing
msg[i].buf[0] without sanity check, null ptr deref would happen. We add
check on msg[i].len to prevent crash.

Similar commit:
commit 0ed554fd76 ("media: dvb-usb: az6027: fix null-ptr-deref in az6027_i2c_xfer()")

Link: https://lore.kernel.org/linux-media/20230313095008.1039689-1-harperchen1110@gmail.com
Signed-off-by: Wei Chen <harperchen1110@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
This commit is contained in:
Wei Chen 2023-03-13 09:50:08 +00:00 committed by Mauro Carvalho Chehab
parent aa4a447b81
commit 9ded5bd2a4
1 changed files with 4 additions and 0 deletions
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4
drivers/media/usb/dvb-usb/digitv.c
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@ -63,6 +63,10 @@ static int digitv_i2c_xfer(struct i2c_adapter *adap,struct i2c_msg msg[],int num
warn("more than 2 i2c messages at a time is not handled yet. TODO.");
for (i = 0; i < num; i++) {
if (msg[i].len < 1) {
i = -EOPNOTSUPP;
break;
}
/* write/read request */
if (i+1 < num && (msg[i+1].flags & I2C_M_RD)) {
if (digitv_ctrl_msg(d, USB_READ_COFDM, msg[i].buf[0], NULL, 0,