bpf: Fix use-after-free in arena_vm_close on fork

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Summary

CVECVE-2026-45837
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-27 11:16:23 UTC
Updated2026-05-27 14:48:03 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: bpf: Fix use-after-free in arena_vm_close on fork arena_vm_open() only bumps vml->mmap_count but never registers the child VMA in arena->vma_list. The vml->vma always points at the parent VMA, so after parent munmap the pointer dangles. If the child then calls bpf_arena_free_pages(), zap_pages() reads the stale vml->vma triggering use-after-free. Fix this by preventing the arena VMA from being inherited across fork with VM_DONTCOPY, and preventing VMA splits via the may_split callback. Also reject mremap with a .mremap callback returning -EINVAL. A same-size mremap(MREMAP_FIXED) on the full arena VMA reaches copy_vma() through the following path: check_prep_vma() - returns 0 early: new_len == old_len skips VM_DONTEXPAND check prep_move_vma() - vm_start == old_addr and vm_end == old_addr + old_len so may_split is never called move_vma() copy_vma_and_data() copy_vma() vm_area_dup() - copies vm_private_data (vml pointer) vm_ops->open() - bumps vml->mmap_count vm_ops->mremap() - returns -EINVAL, rollback unmaps new VMA The refcount ensures the rollback's arena_vm_close does not free the vml shared with the original VMA.

Risk And Classification

EPSS: 0.000180000 probability, percentile 0.048460000 (date 2026-06-01)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 317460317a02a1af512697e6e964298dedd8a163 723b9fa930cc277c15ce6b9ec9feec828cfac9d7 git Not specified
CNA Linux Linux affected 317460317a02a1af512697e6e964298dedd8a163 d18099f19e53250f8ad2801498b88cec29d9107a git Not specified
CNA Linux Linux affected 317460317a02a1af512697e6e964298dedd8a163 201128fcc7b213d27ab77bc4e89488b41796480f git Not specified
CNA Linux Linux affected 317460317a02a1af512697e6e964298dedd8a163 4fddde2a732de60bb97e3307d4eb69ac5f1d2b74 git Not specified
CNA Linux Linux affected 6.9 Not specified
CNA Linux Linux unaffected 6.9 semver Not specified
CNA Linux Linux unaffected 6.12.88 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.30 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.7 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/4fddde2a732de60bb97e3307d4eb69ac5f1d2b74 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/723b9fa930cc277c15ce6b9ec9feec828cfac9d7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/201128fcc7b213d27ab77bc4e89488b41796480f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d18099f19e53250f8ad2801498b88cec29d9107a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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