CVE-2025-39836

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

efi: stmm: Fix incorrect buffer allocation method

The communication buffer allocated by setup_mm_hdr() is later on passed to tee_shm_register_kernel_buf(). The latter expects those buffers to be contiguous pages, but setup_mm_hdr() just uses kmalloc(). That can cause various corruptions or BUGs, specifically since commit 9aec2fb0fd5e ("slab: allocate frozen pages"), though it was broken before as well.

Fix this by using alloc_pages_exact() instead of kmalloc().

This vulnerability does not affect supported Red Hat Enterprise Linux releases because the affected EFI StandaloneMM driver code is not present in shipped kernel builds. The underlying flaw involves improper memory page allocation during EFI communications over the Trusted Execution Environment subsystem in upstream kernels. Because Red Hat Enterprise Linux does not include this driver functionality, there is no operational impact or security risk to supported deployments.