Re: [PATCH 05/24] media: dvb-usb-v2: ec168: fix null-ptr-deref in ec168_i2c_xfer()

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Am 19.05.23 um 11:17 schrieb Wei Chen:
Dear Linux Developers,

Hi Wei,
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?

I think the best is to send new patches on top of the already accepted patches.

Regards
Matthias



Thanks,
Wei


------ Original Message ------
From zzam@xxxxxxxxxx
To "Mauro Carvalho Chehab" <mchehab@xxxxxxxxxx>
Cc "Wei Chen" <harperchen1110@xxxxxxxxx>; "Antti Palosaari" <crope@xxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; linux-media@xxxxxxxxxxxxxxx
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@xxxxxxxxx>

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@xxxxxxxxx
Signed-off-by: Wei Chen <harperchen1110@xxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
---
  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 */





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