ptp: vmclock: prevent read-only mappings from becoming writable

Summary

In the Linux kernel, the following vulnerability has been resolved: ptp: vmclock: prevent read-only mappings from becoming writable vmclock_miscdev_mmap() rejects writable mappings of the shared vmclock ABI page with -EROFS, but leaves VM_MAYWRITE set. Userspace can map the page read-only and then upgrade it to writable with mprotect(), after which the guest can corrupt the host-written timekeeping data (sequence counter, UTC time, TSC offset) that the vmclock ABI defines as read-only. Clear VM_MAYWRITE on the read-only path so the mapping cannot be upgraded, as i915 does for its read-only objects and as fixed in drm/vc4 (CVE-2026-68445) and drm/panthor (CVE-2024-53071).

Timeline

1. Aug 28, 2026, 7:03 AM UTCCVE published
2. Oct 19, 2026, 8:43 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 20503272422693d793b84f88bf23fe4e955d3a33 · fixed in 5b4f2bec7bea6c04084d720d731bedee7caf878d; From 20503272422693d793b84f88bf23fe4e955d3a33 · fixed in 3f5677d2f817355147337f0453174c7bb0f3b66a; From 20503272422693d793b84f88bf23fe4e955d3a33 · fixed in 2496e141827102d6af512950057d402a2cfb2bfc; From 20503272422693d793b84f88bf23fe4e955d3a33 · fixed in 2e596e7814ba38cdc129991058b6c254ed37cb11; From 20503272422693d793b84f88bf23fe4e955d3a33 · fixed in 0ce59c4148ecd1520c5592a63bb3c8991ee2d326; From 20503272422693d793b84f88bf23fe4e955d3a33 · fixed in a5edadbae57e2298a56cf7a4e774a027905a331f

• Linux Linux

  6.13

• KernelLinux

  From 6.13.0 · fixed in 6.18.47; From 6.19.0 · fixed in 6.18.50; fixed in 7.1.11; From 7.2.0 · fixed in 7.2.1; From 7.3.0 · fixed in 7.2.4

References 6