CVE-2026-46042mm/mempolicy: fix memory leaks in weighted_interleave_auto_store()

Official description

In the Linux kernel, the following vulnerability has been resolved: mm/mempolicy: fix memory leaks in weighted_interleave_auto_store() weighted_interleave_auto_store() fetches old_wi_state inside the if (!input) block only. This causes two memory leaks: 1. When a user writes "false" and the current mode is already manual, the function returns early without freeing the freshly allocated new_wi_state. 2. When a user writes "true", old_wi_state stays NULL because the fetch is skipped entirely. The old state is then overwritten by rcu_assign_pointer() but never freed, since the cleanup path is gated on old_wi_state being non-NULL. A user can trigger this repeatedly by writing "1" in a loop. Fix both leaks by moving the old_wi_state fetch before the input check, making it unconditional. This also allows a unified early return for both "true" and "false" when the requested mode matches the current mode. Reviewed by: Donet Tom <donettom@linux.ibm.com>

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/c42a7efb9060d89b72708ffaf255d0002c2164a7
• https://git.kernel.org/stable/c/39caa9ca863f96b3d00447c5aa200cabda489856
• https://git.kernel.org/stable/c/6fae274ce0e3109cbbc4c18b354eaace1f0af7d7