Linux vulnerability

What happened

In the Linux kernel, the following vulnerability has been resolved: selinux: fix overlayfs mmap() and mprotect() access checks The existing SELinux security model for overlayfs is to allow access if the current task is able to access the top level file (the "user" file) and the mounter's credentials are sufficient to access the lower level file (the "backing" file). Unfortunately, the current code does not properly enforce these access controls for both mmap() and mprotect() operations on overlayfs filesystems. This patch makes use of the newly created security_mmap_backing_file() LSM hook to provide the missing backing file enforcement for mmap() operations, and leverages the backing file API and new LSM blob to provide the necessary information to properly enforce the mprotect() access controls.

Affected versions

Linux: 2f502839e85ab265f03f25f30d6463154aee5473 through before bc6c380c1159de52a252ed11f19a42c47f60a735 (git); 2f502839e85ab265f03f25f30d6463154aee5473 through before 8bacd09f12c27710228562e4d13163e58c5f4a45 (git); 2f502839e85ab265f03f25f30d6463154aee5473 through before d844702198395d3f80222777030f69db6be6b709 (git); 2f502839e85ab265f03f25f30d6463154aee5473 through before cd0e707a927a70cdfd8bc5a512a9719a87f5ed51 (git); 2f502839e85ab265f03f25f30d6463154aee5473 through before 82544d36b1729153c8aeb179e84750f0c085d3b1 (git); 4.19 Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.