Executive brief
The Linux kernel contained an outdated validation check in the pagemap code that reports memory layout information to user applications. The check incorrectly assumed only migration entries could appear at a certain memory level, but this assumption became false after support for device-private memory entries was added. Removing this stale assertion prevents false warning messages and improves system stability.
Technical details
The vulnerability is a stale assertion (VM_WARN_ON_ONCE) in fs/proc/task_mmu.c within the pagemap_pmd_range_thp() function. The code incorrectly warned if a non-present PMD entry was not a migration entry, but this assumption became invalid once device-private entries at the PMD level were introduced by commit a30b48bf1b24. The fix simply removes the outdated assertion. No authentication is required; the pagemap interface is user-accessible. This is a code correctness issue rather than a security vulnerability, and the fix has been merged into the upstream kernel.
Affected products
- Linux Linux kernel multiple versions prior to the fix
Timeline
- 2026-06-04: other: Patch authored by Dev Jain
- 2026-06-08: other: Patch merged into linux-next
- 2026-07-24: patched: Patch included in stable kernel release