High [CVE-2026-52971] Fix potential use-after-free in get_timestamp

In the Linux kernel, the following vulnerability has been resolved: net: ena: PHC: Fix potential use-after-free in get_timestamp Move the phc->active check and resp pointer assignment to after acquiring the spinlock. Previously, phc->active was checked without holding the lock, and resp was cached from ena_dev->phc.virt_addr before the lock was acquired.

If ena_com_phc_destroy() runs between the lockless active check and the lock acquisition, it sets active=false, releases the lock, frees the DMA memory, and sets virt_addr=NULL. The get_timestamp path would then read a NULL virt_addr and dereference it.

With both the active check and the pointer read under the lock, destroy cannot free the memory while get_timestamp is using it. A flaw was found in the Linux kernel's Elastic Network Adapter (ENA) driver, specifically within the Precision Time Protocol Hardware Clock (PHC) timestamp retrieval function.

A race condition exists where the `get_timestamp` function could attempt to access memory that has already been freed by the `ena_com_phc_destroy` function. This use-after-free vulnerability can lead to a NULL pointer dereference, potentially causing a system crash and resulting in a Denial of Service (DoS).

Red Hat severity: Moderate — CVSS 7 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H). Weakness: CWE-825.