Bug 2521428 (CVE-2026-74716)

Summary: CVE-2026-74716 kernel: accel/amdxdna: Fix locally exploitable BUG_ON in amdxdna_insert_pages()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's amdxdna graphics driver. An unprivileged local user could exploit a vulnerability in how the driver handles memory management operations. By performing specific memory mapping and access patterns, a user could trigger an assertion failure, leading to a system crash and a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-08-22 15:45:07 UTC 
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.
Comment 1 Keith Grant 2026-08-24 17:58:52 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026082239-CVE-2026-74716-b277@gregkh/T