selinux: preserve user SID across nested backing files
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 6.6.158, 6.12.112, 6.18.54, 7.1, 7.2.8
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
In the Linux kernel, the following vulnerability has been resolved: selinux: preserve user SID across nested backing files SELinux saves the user file SID in a backing-file security blob so it remains available after mmap() replaces vma->vm_file with a backing file. For nested backing files (overlayfs over overlayfs, or FUSE passthrough backed by overlayfs), user_file may itself be a backing file. Its fsec->sid is the SID of the mounter that opened it, rather than the user that opened the top-level file. mprotect() then checks fd { use } against the mounter SID. This can incorrectly deny access without a domain transition, or check the wrong target SID after one. Copy the saved user SID when user_file is a backing file. Keep using the regular file SID for the first backing layer. With two nested overlayfs mounts and SELinux enforcing, mprotect(PROT_READ) returns EACCES with an fd { use } denial against the mounter SID. With this change, mprotect() succeeds. Tested on arm64 QEMU with a small BusyBox initramfs and a purpose-built SELinux policy. The original test was also repeated with Fedora Cloud Base 44 userspace and gave the same result.
Timeline
- CVE published
- Record last updated
Affected versions
- Linux Linux
From bc6c380c1159de52a252ed11f19a42c47f60a735 · fixed in caa1b913d90d5dc07073733326d2af0f0288f089; From 8bacd09f12c27710228562e4d13163e58c5f4a45 · fixed in 6aaeec59aadcd1eafc18b049f1b759fb6b9d9569; From d844702198395d3f80222777030f69db6be6b709 · fixed in 9d99b770e7b67b00bdef9005b928aad13e1d679b; From 82544d36b1729153c8aeb179e84750f0c085d3b1 · fixed in ff20d16b2e8230c034e21540043df47222dcc09b; From 82544d36b1729153c8aeb179e84750f0c085d3b1 · fixed in 8c0c602202b9a4909b00bc3354e3c0355bc69e65; From 6.6.144 · fixed in 6.6.158; From 6.12.95 · fixed in 6.12.112; From 6.18.38 · fixed in 6.18.54; From 7.0.4 · fixed in 7.1
- Linux Linux
7.1
- KernelLinux
fixed in 6.6.158; From 6.7.0 · fixed in 6.12.112; From 6.13.0 · fixed in 6.18.54; From 6.19.0 · fixed in 7.2.8