selinux: recheck intermediate backing files on mprotect()

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Summary

CVECVE-2026-98214
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-06 09:18:07 UTC
Updated2026-10-06 09:18:07 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: selinux: recheck intermediate backing files on mprotect() mprotect() can be used to bypass the SELinux checks that mmap() performs against the intermediate layers of a stacked filesystem. mmap() checks every backing layer as the request descends through the stack. mprotect() only has the lowest backing file in vma->vm_file, so it rechecks the top-level user and the lowest mounter, but skips the mounters of every layer in between. With two nested overlayfs mounts and a policy denying mounter_t -> middle_file_t:file { execute }, a direct mmap(PROT_EXEC) is denied: avc: denied { execute } for pid=71 comm="nested_exec" path="/payload" dev="overlay" ino=9 scontext=user_u:base_r:mounter_t tcontext=user_u:object_r:middle_file_t tclass=file permissive=0 while mmap(PROT_NONE) followed by mprotect(PROT_EXEC) succeeds. Preserve each intermediate path, mounter SID and file-description SID in the backing-file security blob, copying the saved entries when another backing layer is opened. Allocate the array only for nested backing files, and release it and the path references in the backing_file_free hook. During mprotect(), recheck fd { use } and the requested inode permissions for every saved mounter, and include the intermediate layers in the execmod checks. Policy for nested stacking may then need to grant intermediate mounters what a direct mmap() already requires, and execmod on intermediate labels for binaries using text relocations. Tested on arm64 QEMU with a small BusyBox initramfs and a purpose-built SELinux policy, on a mainline tree containing commit f2381b546e7e ("fs: fix user path of nested backing files"). [PM: subject tweak]

Risk And Classification

EPSS: 0.002190000 probability, percentile 0.112830000 (date 2026-10-06)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected bc6c380c1159de52a252ed11f19a42c47f60a735 4d50ebe5a27724e020747ffd61a051dec67cb8ec git Not specified
CNA Linux Linux affected 8bacd09f12c27710228562e4d13163e58c5f4a45 89376fbfdcc1a728e1775f98752cdd90b0930a00 git Not specified
CNA Linux Linux affected d844702198395d3f80222777030f69db6be6b709 d127c7e1f3e1231d8ac8b2738e3f00bea12afe74 git Not specified
CNA Linux Linux affected 82544d36b1729153c8aeb179e84750f0c085d3b1 c2bbb905af2293549651b614a52ad91e0b462b60 git Not specified
CNA Linux Linux affected 82544d36b1729153c8aeb179e84750f0c085d3b1 78fc54b934bfb2c18aad8154c7302067146946f9 git Not specified
CNA Linux Linux affected cd0e707a927a70cdfd8bc5a512a9719a87f5ed51 git Not specified
CNA Linux Linux affected 6.6.144 6.6.158 semver Not specified
CNA Linux Linux affected 6.12.95 6.12.112 semver Not specified
CNA Linux Linux affected 6.18.38 6.18.54 semver Not specified
CNA Linux Linux affected 7.0.4 7.1 semver Not specified
CNA Linux Linux affected 7.1 Not specified
CNA Linux Linux unaffected 7.1 semver Not specified
CNA Linux Linux unaffected 6.6.158 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.112 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.54 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.8 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc4 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/78fc54b934bfb2c18aad8154c7302067146946f9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d127c7e1f3e1231d8ac8b2738e3f00bea12afe74 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/89376fbfdcc1a728e1775f98752cdd90b0930a00 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c2bbb905af2293549651b614a52ad91e0b462b60 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/4d50ebe5a27724e020747ffd61a051dec67cb8ec 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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