Linux hwe edge: In the Linux kernel, the following vulnerability has been resolved: serial: qcom-geni: fix TX DMA buffer flush When transmit flushing a qcom-geni… (CVE-2026-74655)

The Linux kernel's qcom-geni UART driver had a flaw where flushing the transmit buffer during an ongoing TX DMA caused the UART to hang by infinitely repeating corrupted DMA frames. The root cause was the absence of a flush_buffer callback in DMA-mode uart_ops, allowing in-flight transfers to complete after the transmit FIFO was reset, causing underflows and repeated transfers. Additionally, the stop path incorrectly unmapped buffers while still in use and failed to reset the TX DMA state machine properly. The fix involved adding a flush_buffer callback to stop transfers and clear internal counters, properly canceling the main sequencer command, resetting the state machine, and ensuring buffer cleanup. This bug can be triggered from userspace with a large write immediately followed by TCOFLUSH, causing tcdrain to hang indefinitely. The fix was validated on Arduino Uno Q (QRB2210) using /dev/ttyHS1.

Exploitation of this vulnerability can cause the UART to hang indefinitely during transmit buffer flushing, leading to denial of service conditions where serial communication is blocked. This affects confidentiality, integrity, and availability of data transmitted via the affected UART interface. The CVSS score is 8.8, indicating high severity impact on confidentiality, integrity, and availability. No known exploits in the wild have been reported.

A fix for this vulnerability has been implemented in the Linux kernel. Users should update to the patched kernel version that includes the fix for CVE-2026-74655. Since this is a kernel-level issue, applying the official kernel update from the Linux distribution vendor is the recommended remediation. No additional mitigations are indicated by the vendor advisory.