BaseFortify

Publication date: 2025-10-04

Last updated on: 2025-10-06

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: zram: fix slot write race condition Parallel concurrent writes to the same zram index result in leaked zsmalloc handles. Schematically we can have something like this: CPU0 CPU1 zram_slot_lock() zs_free(handle) zram_slot_lock() zram_slot_lock() zs_free(handle) zram_slot_lock() compress compress handle = zs_malloc() handle = zs_malloc() zram_slot_lock zram_set_handle(handle) zram_slot_lock zram_slot_lock zram_set_handle(handle) zram_slot_lock Either CPU0 or CPU1 zsmalloc handle will leak because zs_free() is done too early. In fact, we need to reset zram entry right before we set its new handle, all under the same slot lock scope.

CVSS Scores

EPSS Scores

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Meta Information

Published

2025-10-04

Last Modified

2025-10-06

Generated

2026-07-06

AI Q&A

2025-10-04

EPSS Evaluated

2026-07-05

NVD

CVE-2025-39941

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	From 5.15.160 (inc) to 5.16 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability is a race condition in the Linux kernel's zram module where parallel concurrent writes to the same zram index cause leaked zsmalloc handles. The issue occurs because zs_free() is called too early during concurrent operations, leading to one of the handles being leaked. The fix involves resetting the zram entry right before setting its new handle, all within the same slot lock scope to prevent the race condition.

Impact Analysis

The vulnerability can lead to leaked memory handles (zsmalloc handles) due to race conditions during concurrent writes in the zram module. This can cause resource leaks, potentially degrading system performance or stability over time if the leaked handles accumulate.

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