CVE-2026-53153mm/list_lru: drain before clearing xarray entry on reparent

Official description

In the Linux kernel, the following vulnerability has been resolved: mm/list_lru: drain before clearing xarray entry on reparent memcg_reparent_list_lrus() clears the dying memcg's xarray entry with xas_store(&xas, NULL) before reparenting its per-node lists into the parent. This opens a window where a concurrent list_lru_del() arriving for the dying memcg sees xa_load() == NULL, walks to the parent in lock_list_lru_of_memcg(), takes the parent's per-node lock, and calls list_del_init() on an item still physically linked on the dying memcg's list. If another in-flight thread holds the dying memcg's per-node lock at the same moment (another list_lru_del, or a list_lru_walk_one running an isolate callback), both threads modify ->next/->prev pointers on the same physical list under different locks. Adjacent items can corrupt each other's links. Fix it by reversing the order: reparent each per-node list and mark the child's list lru dead and then clear the xarray entry. Any concurrent list_lru op that finds the still-set xarray entry either takes the dying memcg's per-node lock (synchronizing with the drain) or sees LONG_MIN and walks to the parent, where the items now live.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/c19ff4351214f059349788e13e70e74325831ff6
• https://git.kernel.org/stable/c/2b66496d794e98f7aeec7688573051f22ec40bac
• https://git.kernel.org/stable/c/98733f3f0becb1ae0701d021c1748e974e5fa55c
• https://access.redhat.com/security/cve/CVE-2026-53153 vdb-entry, x_refsource_REDHAT
• RHBZ#2492790 issue-tracking, x_refsource_REDHAT
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53153.json x_sadp-csaf-vex
• https://access.redhat.com/errata/RHSA-2026:61887 vendor-advisory, x_refsource_REDHAT