CVE-2021-47434

/// Technical 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.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References