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CVE PROGRAM SOURCE RECORDUnscored

CVE-2026-98214

selinux: recheck intermediate backing files on mprotect()

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In 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]

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • bc6c380c1159de52a252ed11f19a42c47f60a735 to < 4d50ebe5a27724e020747ffd61a051dec67cb8ecaffected
  • 8bacd09f12c27710228562e4d13163e58c5f4a45 to < 89376fbfdcc1a728e1775f98752cdd90b0930a00affected
  • d844702198395d3f80222777030f69db6be6b709 to < d127c7e1f3e1231d8ac8b2738e3f00bea12afe74affected
  • 82544d36b1729153c8aeb179e84750f0c085d3b1 to < c2bbb905af2293549651b614a52ad91e0b462b60affected
  • 82544d36b1729153c8aeb179e84750f0c085d3b1 to < 78fc54b934bfb2c18aad8154c7302067146946f9affected
  • cd0e707a927a70cdfd8bc5a512a9719a87f5ed51affected
  • 6.6.144 to < 6.6.158affected
  • 6.12.95 to < 6.12.112affected
  • 6.18.38 to < 6.18.54affected
  • 7.0.4 to < 7.1affected

Linux Linux

Default version status: affected

  • 7.1affected
  • 0 to < 7.1unaffected
  • 6.6.158 to ≤ 6.6.*unaffected
  • 6.12.112 to ≤ 6.12.*unaffected
  • 6.18.54 to ≤ 6.18.*unaffected
  • 7.2.8 to ≤ 7.2.*unaffected
  • 7.3 to ≤ *unaffected

References