Linux Kernel up to 7.1.7 mglru reset_batch_size race condition

Summaryinfo

A vulnerability described as critical has been identified in Linux Kernel up to 7.1.7. This affects the function reset_batch_size of the component mglru. Executing a manipulation can lead to race condition. This vulnerability is handled as CVE-2026-80719. It is possible to launch the attack on the local host. There is not any exploit available.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.1.7. It has been declared as critical. This vulnerability affects the function reset_batch_size of the component mglru. The manipulation with an unknown input leads to a race condition vulnerability. The CWE definition for the vulnerability is CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. As an impact it is known to affect availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: mm: mglru: fix stale batch updates after memcg reparenting The mglru page table walker batches per-generation size deltas in walk->nr_pages while walking page tables without holding the lruvec lock. The reset_batch_size() later folds those deltas into walk->lruvec under the lruvec lock. The page table walker can run concurrently with the memcg reparenting path as follows: CPU0 CPU1 ==== ==== walk_mm --> walk_page_range --> update_batch_size --> walk->nr_pages += delta mem_cgroup_css_offline --> memcg_reparent_objcgs --> lock lruvec lru_gen_reparent_memcg --> reparent child folios to parent unlock lruvec lock lruvec reset_batch_size --> child lrugen->nr_pages += delta This will trigger the following warning in lru_gen_exit_memcg(): VM_WARN_ON_ONCE(memchr_inv(lruvec->lrugen.nr_pages, 0, sizeof(lruvec->lrugen.nr_pages))); And the user-visible impact of underestimated nr_pages in MGLRU was premature OOMs because MGLRU does not try to reclaim memory when nr_pages reaches zero, but there are still more pages. To fix it, make reset_batch_size() check CSS_DYING under RCU before flushing the pending batch. A non-dying memcg keeps the original lruvec stable against RCU-delayed offlining; a dying memcg redirects the deltas to the first non-dying ancestor.

The advisory is available at git.kernel.org. This vulnerability was named CVE-2026-80719 since 08/26/2026. The exploitation appears to be easy. Local access is required to approach this attack. Technical details are known, but there is no available exploit.

Upgrading to version 7.1.8 eliminates this vulnerability. Applying the patch fceb6b7f3ddec6ea9fc11577f4cf1b2da73a3101 is able to eliminate this problem.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.1.0
• 7.1.1
• 7.1.2
• 7.1.3
• 7.1.4
• 7.1.5
• 7.1.6
• 7.1.7

License

• open-source

Website

• Vendor: https://www.kernel.org/

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