media: az6007: Fix null-ptr-deref in az6007_i2c_xfer()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: media: az6007: Fix null-ptr-deref in az6007_i2c_xfer() In az6007_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 az6007_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 0ed554fd769a ("media: dvb-usb: az6027: fix null-ptr-deref in az6027_i2c_xfer()")

References

• https://git.kernel.org/stable/c/c6763fefa267f6e62595a6ac1f57815d99fc90b7
• https://git.kernel.org/stable/c/adcb73f8ce9aec48b1f85223f401c1574015d8d2
• https://git.kernel.org/stable/c/991c77fe18c6f374bbf83376f8c42550aa565662
• https://git.kernel.org/stable/c/a9def3e9718a4dc756f48db147d42ec41a966240
• https://git.kernel.org/stable/c/5b1ea100ad3695025969dc4693f307877fb688d6
• https://git.kernel.org/stable/c/6ab7ea4e17d6a605d05308adf8f3408924770cba
• https://git.kernel.org/stable/c/a1110f19d4940e4185251d072cbb0ff51486a1e7
• https://git.kernel.org/stable/c/1047f9343011f2cedc73c64829686206a7e9fc3f