CVE-2026-74716

Summary

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

accel/amdxdna: Fix locally exploitable BUG_ON in amdxdna_insert_pages()

In amdxdna_insert_pages(), vm_flags_mod() sets VM_MIXEDMAP and clears VM_PFNMAP. If an unprivileged userspace process mmaps a non-imported GEM object and then calls madvise(MADV_DONTNEED), the PTEs will be successfully cleared because VM_MIXEDMAP allows this (unlike VM_PFNMAP).

When userspace subsequently accesses the memory, drm_gem_shmem_fault() handles the page fault and attempts to map the backing shmem page via vmf_insert_pfn() which calls vmf_insert_pfn_prot(). Because the backing shmem page is normal system memory (pfn_valid(pfn) is true) and the VMA now has VM_MIXEDMAP set, won't this predictably trigger the explicit assertion BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn))

Fix by removing the vm_flags_mod() call and replacing the vm_insert_pages() pre-population with the handle_mm_fault() loop that was already used for the import (dma-buf) path.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/13339132d89d00b513dff0730bff3a313b9b13b5
• https://git.kernel.org/stable/c/4a19f7ab5972ef608b31ae921419bc3e04b3f8ad

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