Vulnerability CVE-2021-47434
Published: 2024-05-22

Description:
In the Linux kernel, the following vulnerability has been resolved:

xhci: Fix command ring pointer corruption while aborting a command

The command ring pointer is located at [6:63] bits of the command
ring control register (CRCR). All the control bits like command stop,
abort are located at [0:3] bits. While aborting a command, we read the
CRCR and set the abort bit and write to the CRCR. The read will always
give command ring pointer as all zeros. So we essentially write only
the control bits. Since we split the 64 bit write into two 32 bit writes,
there is a possibility of xHC command ring stopped before the upper
dword (all zeros) is written. If that happens, xHC updates the upper
dword of its internal command ring pointer with all zeros. Next time,
when the command ring is restarted, we see xHC memory access failures.
Fix this issue by only writing to the lower dword of CRCR where all
control bits are located.

 References:
https://git.kernel.org/stable/c/22bcb65ea41072ab5d03c0c6290e04e0df6d09a0
https://git.kernel.org/stable/c/62c182b5e763e5f4062e72678e72ce3e02dd4d1b
https://git.kernel.org/stable/c/01c2dcb67e71c351006dd17cbba86c26b7f61eaf
https://git.kernel.org/stable/c/dec944bb7079b37968cf69c8a438f91f15c4cc61
https://git.kernel.org/stable/c/e54abefe703ab7c4e5983e889babd1447738ca42
https://git.kernel.org/stable/c/ff0e50d3564f33b7f4b35cadeabd951d66cfc570
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