The patch titled Subject: mm: multi-gen LRU: fix crash during cgroup migration has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-multi-gen-lru-fix-crash-during-cgroup-migration.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Yu Zhao yuzhao@google.com Subject: mm: multi-gen LRU: fix crash during cgroup migration Date: Sun, 15 Jan 2023 20:44:05 -0700

lru_gen_migrate_mm() assumes lru_gen_add_mm() runs prior to itself. This isn't true for the following scenario:

CPU 1 CPU 2

clone() cgroup_can_fork() cgroup_procs_write() cgroup_post_fork() task_lock() lru_gen_migrate_mm() task_unlock() task_lock() lru_gen_add_mm() task_unlock()

And when the above happens, kernel crashes because of linked list corruption (mm_struct->lru_gen.list).

Link: https://lore.kernel.org/r/20230115134651.30028-1-msizanoen@qtmlabs.xyz/ Link: https://lkml.kernel.org/r/20230116034405.2960276-1-yuzhao@google.com Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks") Signed-off-by: Yu Zhao yuzhao@google.com Reported-by: msizanoen msizanoen@qtmlabs.xyz Tested-by: msizanoen msizanoen@qtmlabs.xyz Cc: stable@vger.kernel.org [6.1+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

--- a/mm/vmscan.c~mm-multi-gen-lru-fix-crash-during-cgroup-migration +++ a/mm/vmscan.c @@ -3323,13 +3323,16 @@ void lru_gen_migrate_mm(struct mm_struct if (mem_cgroup_disabled()) return;

+ /* migration can happen before addition */ + if (!mm->lru_gen.memcg) + return; + rcu_read_lock(); memcg = mem_cgroup_from_task(task); rcu_read_unlock(); if (memcg == mm->lru_gen.memcg) return;

- VM_WARN_ON_ONCE(!mm->lru_gen.memcg); VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list));

lru_gen_del_mm(mm); _

Patches currently in -mm which might be from yuzhao@google.com are

mm-multi-gen-lru-fix-crash-during-cgroup-migration.patch mm-multi-gen-lru-rename-lru_gen_struct-to-lru_gen_folio.patch mm-multi-gen-lru-rename-lrugen-lists-to-lrugen-folios.patch mm-multi-gen-lru-remove-eviction-fairness-safeguard.patch mm-multi-gen-lru-remove-aging-fairness-safeguard.patch mm-multi-gen-lru-shuffle-should_run_aging.patch mm-multi-gen-lru-per-node-lru_gen_folio-lists.patch mm-multi-gen-lru-clarify-scan_control-flags.patch mm-multi-gen-lru-simplify-arch_has_hw_pte_young-check.patch mm-add-vma_has_recency.patch mm-support-posix_fadv_noreuse.patch