media: dvb-usb: az6027: fix null-ptr-deref in az6027_i2c_xfer()

Wei Chen reports a kernel bug as blew:

general protection fault, probably for non-canonical address
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
...
Call Trace:
<TASK>
__i2c_transfer+0x77e/0x1930 drivers/i2c/i2c-core-base.c:2109
i2c_transfer+0x1d5/0x3d0 drivers/i2c/i2c-core-base.c:2170
i2cdev_ioctl_rdwr+0x393/0x660 drivers/i2c/i2c-dev.c:297
i2cdev_ioctl+0x75d/0x9f0 drivers/i2c/i2c-dev.c:458
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0xfb/0x170 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fd834a8bded

In az6027_i2c_xfer(), if msg[i].addr is 0x99,
a null-ptr-deref will caused when accessing msg[i].buf.
For msg[i].len is 0 and msg[i].buf is null.

Fix this by checking msg[i].len in az6027_i2c_xfer().

Link: https://lore.kernel.org/lkml/CAO4mrfcPHB5aQJO=mpqV+p8mPLNg-Fok0gw8gZ=zemAfMGTzMg@mail.gmail.com/
Link: https://lore.kernel.org/linux-media/20221120065918.2160782-1-zhongbaisong@huawei.com
Fixes: 76f9a820c867 ("V4L/DVB: AZ6027: Initial import of the driver")
Reported-by: Wei Chen <harperchen1110@gmail.com>
Signed-off-by: Baisong Zhong <zhongbaisong@huawei.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

diff --git a/drivers/media/usb/dvb-usb/az6027.c b/drivers/media/usb/dvb-usb/az6027.c
index cf15988dfb5103c80737fff4c509a0a799ed228d..7d78ee09be5e1dc40d813777d5e26e2abeb8aba3 100644 (file)
--- a/drivers/media/usb/dvb-usb/az6027.c
+++ b/drivers/media/usb/dvb-usb/az6027.c
@@ -975,6 +975,10 @@ static int az6027_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[], int n
                if (msg[i].addr == 0x99) {
                        req = 0xBE;
                        index = 0;
+                       if (msg[i].len < 1) {
+                               i = -EOPNOTSUPP;
+                               break;
+                       }
                        value = msg[i].buf[0] & 0x00ff;
                        length = 1;
                        az6027_usb_out_op(d, req, value, index, data, length);