CVE-2026-97931

Summary

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

ALSA: us122l: Prevent write upgrades for read mappings

The hwdep mmap callback rejects read-buffer mappings that are initially writable, but leaves VM_MAYWRITE set on mappings created with PROT_READ. A process that can open the hwdep node O_RDWR can later use mprotect() to make the mapping writable.

The read allocation begins with struct usb_stream. Its read_size member is used by the fault handler to decide which pages belong to the read buffer. The read VMA intentionally remains expandable because pcm_usb_stream uses mremap() after reading that size. Changing read_size first can therefore map and access pages beyond the allocation. The same member is also consumed by usb_stream_free(), where changing it can make free_pages_exact() release pages outside the allocation.

Clear VM_MAYWRITE for read-buffer mappings after rejecting an initially writable VMA. This keeps the separate output-buffer mapping writable while preventing later permission upgrades.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/64a87950239867682cde128020e1a47088295e5c
• https://git.kernel.org/stable/c/d9c537b14f4982f17b103e3a2cfeee4bee6bc026
• https://git.kernel.org/stable/c/0eb9dd4774af0ac4d1fd105ef2b0a1f6cec06f2f
• https://git.kernel.org/stable/c/71c610aeb1770302ac9c9e0b9a4ecd37f1311928

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