CVE-2026-93096cxl/features: Serialize multi-part Get/Set Feature transfers

Official description

In the Linux kernel, the following vulnerability has been resolved: cxl/features: Serialize multi-part Get/Set Feature transfers A Get or Set Feature payload larger than the mailbox payload size is split into several mailbox commands. mbox_mutex only serializes individual mailbox commands and is dropped between iterations of these loops. Nothing serializes the multi-part transfer as a whole. cxl_get_feature() and cxl_set_feature() are reachable concurrently from fwctl (per-fd RPCs run under a read-held registration lock) and from the EDAC scrub/ECS/repair paths, so two transfers to the same mailbox can interleave their parts and corrupt the device's transfer context. Add a per-mailbox feat_mutex and hold it across the whole transfer in both functions. It nests outside mbox_mutex (which is taken inside cxl_internal_send_cmd()), and is taken nowhere else, so no lock-ordering inversion is introduced.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/c6492e17412048387435f256ffafc4dd6518db28
• https://git.kernel.org/stable/c/7682b617db1f19bc606b5f1badadcf1e63a87b14
• https://git.kernel.org/stable/c/77b814c1832fde018c30357b4ec3fcdaa91a1c10