misc: nsm: bound the device-reported response length

Overview

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

misc: nsm: bound the device-reported response length

nsm_sendrecv_msg_locked() stores the virtqueue used-ring length reported by the NSM device into msg->resp.len without bounding it to the response buffer. A malicious or buggy backend can report a length larger than the response buffer; parse_resp_raw() then copies that many bytes out of the fixed buffer to user space, disclosing adjacent kernel heap (an out-of-bounds read). The request path already floors its length in fill_req_raw(); the response path lacks the symmetric check.

Clamp the stored length to the size of the response buffer. Well-behaved devices report no more than the posted buffer size, so conforming traffic is unaffected.

Affected

• Linux >= b9873755a6c8ccfce79094c4dce9efa3ecb1a749 < 339f19b9a6171289b0e797deb8bda80b9a1fcc30
• Linux >= b9873755a6c8ccfce79094c4dce9efa3ecb1a749 < 29e634a18957acda11383a15ab98a91c4ae9e294
• Linux >= b9873755a6c8ccfce79094c4dce9efa3ecb1a749 < 2aa0fb9c96f894a9c179a48e7522ea6705800adf
• Linux >= b9873755a6c8ccfce79094c4dce9efa3ecb1a749 < 808e530654a5354e6df78863a5d61e4d44e67235
• Linux 6.8

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Vendor advisories

• Red Hat VEX · Moderate · updated 2026-09-21 · vex