linux-kernel - Re: [PATCH 05/24] media: dvb-usb-v2: ec168: fix null-ptr-deref in ec168_i2c

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Message-Id: <em460c2fef-d14b-4cd9-97dd-ef7b52090a48@bb0cba59.com>
Date:   Fri, 19 May 2023 09:17:10 +0000
From:   "Wei Chen" <harperchen1110@...il.com>
To:     zzam@...too.org, "Mauro Carvalho Chehab" <mchehab@...nel.org>
Cc:     "Antti Palosaari" <crope@....fi>, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org
Subject: Re: [PATCH 05/24] media: dvb-usb-v2: ec168: fix null-ptr-deref in
 ec168_i2c_xfer()

Dear Linux Developers,

Thank you for the review for my patch in driver az6027 and ec168.

Yes, I agree with you. Sorry for my mistake. Since these two patches has already been accepted and merged in git tree media, should I send a new patch to revise this problem? Or how could I revise an accepted patch?

Thanks,
Wei


------ Original Message ------
>From zzam@...too.org
To "Mauro Carvalho Chehab" <mchehab@...nel.org>
Cc "Wei Chen" <harperchen1110@...il.com>; "Antti Palosaari" <crope@....fi>; linux-kernel@...r.kernel.org; linux-media@...r.kernel.org
Date 2023/5/17 13:10:34
Subject Re: [PATCH 05/24] media: dvb-usb-v2: ec168: fix null-ptr-deref in ec168_i2c_xfer()

>Am 13.05.23 um 19:57 schrieb Mauro Carvalho Chehab:
>>From: Wei Chen <harperchen1110@...il.com>
>>
>>In ec168_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.
>>If accessing msg[i].buf[0] without sanity check, null pointer deref
>>would happen. We add check on msg[i].len to prevent crash.
>>
>>Similar commit:
>>commit 0ed554fd769a ("media: dvb-usb: az6027: fix null-ptr-deref in az6027_i2c_xfer()")
>>
>Review comment below.
>
>>Link: https://lore.kernel.org/linux-media/20230313085853.3252349-1-harperchen1110@gmail.com
>>Signed-off-by: Wei Chen <harperchen1110@...il.com>
>>Signed-off-by: Mauro Carvalho Chehab <mchehab@...nel.org>
>>---
>>   drivers/media/usb/dvb-usb-v2/ec168.c | 12 ++++++++++++
>>   1 file changed, 12 insertions(+)
>>
>>diff --git a/drivers/media/usb/dvb-usb-v2/ec168.c b/drivers/media/usb/dvb-usb-v2/ec168.c
>>index 7ed0ab9e429b..0e4773fc025c 100644
>>--- a/drivers/media/usb/dvb-usb-v2/ec168.c
>>+++ b/drivers/media/usb/dvb-usb-v2/ec168.c
>>@@ -115,6 +115,10 @@ static int ec168_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
>>   	while (i < num) {
>>   		if (num > i + 1 && (msg[i+1].flags & I2C_M_RD)) {
>>   			if (msg[i].addr == ec168_ec100_config.demod_address) {
>>+				if (msg[i].len < 1) {
>>+					i = -EOPNOTSUPP;
>>+					break;
>>+				}
>>   				req.cmd = READ_DEMOD;
>>   				req.value = 0;
>>   				req.index = 0xff00 + msg[i].buf[0]; /* reg */
>>@@ -131,6 +135,10 @@ static int ec168_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
>>   			}
>>   		} else {
>>   			if (msg[i].addr == ec168_ec100_config.demod_address) {
>>+				if (msg[i].len < 1) {
>>+					i = -EOPNOTSUPP;
>>+					break;
>>+				}
>The check condition should be msg[i].len < 2 or != 2. The following lines access msg[i].buf elements 0 and 1.
>>   				req.cmd = WRITE_DEMOD;
>>   				req.value = msg[i].buf[1]; /* val */
>>   				req.index = 0xff00 + msg[i].buf[0]; /* reg */
>>@@ -139,6 +147,10 @@ static int ec168_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
>>   				ret = ec168_ctrl_msg(d, &req);
>>   				i += 1;
>>   			} else {
>>+				if (msg[i].len < 1) {
>>+					i = -EOPNOTSUPP;
>>+					break;
>>+				}
>>   				req.cmd = WRITE_I2C;
>>   				req.value = msg[i].buf[0]; /* val */
>>   				req.index = 0x0100 + msg[i].addr; /* I2C addr */
>