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/mm-multi-gen-lru-fix-crash-during-cgroup-migration.patch
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@xxxxxxxxxx>
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@xxxxxxxxxxx/
Link: https://lkml.kernel.org/r/20230116034405.2960276-1-yuzhao@xxxxxxxxxx
Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks")
Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Reported-by: msizanoen <msizanoen@xxxxxxxxxxx>
Tested-by: msizanoen <msizanoen@xxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [6.1+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- 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@xxxxxxxxxx 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
