In the Linux kernel, the following vulnerability has been resolved: x86/mm: Drop unnecessary PMD page copy when freeing On a box with a discrete… (CVE-2026-98939)

The vulnerability (CVE-2026-98939) in the Linux kernel's x86 memory management subsystem involved an unnecessary PMD page copy operation during page freeing. On systems with discrete GPUs, this triggered a circular locking dependency detected by lockdep, causing potential deadlocks when the TTM page pool was shrunk by kswapd. The root cause was an mmap_read_lock added to kernel page protection code, conflicting with GFP_KERNEL allocations during page table free paths. The fix removes the PMD copy, detaches the PMD page at the PUD level, flushes mid-level caches, and frees PTE tables directly from the detached PMD page, avoiding allocations and thus resolving the locking issue.

The vulnerability could cause a kernel deadlock on systems with discrete GPUs during memory reclaim operations, potentially leading to system hangs or degraded performance. There is no indication of code execution or privilege escalation from the provided data.

A fix has been implemented in the Linux kernel that removes the problematic PMD page copy and associated locking issue. Users should update to the fixed kernel version once available. No additional mitigation steps are indicated.