Bug 2395796 (CVE-2025-39836)

Summary: CVE-2025-39836 kernel: efi: stmm: Fix incorrect buffer allocation method
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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OS: Linux   
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Description OSIDB Bzimport 2025-09-16 14:03:06 UTC
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().