The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8f0b36497303487d5a32c75789c77859cc2ee895 Mon Sep 17 00:00:00 2001 From: Muchun Song songmuchun@bytedance.com Date: Fri, 1 Apr 2022 11:28:36 -0700 Subject: [PATCH] mm: kfence: fix objcgs vector allocation

If the kfence object is allocated to be used for objects vector, then this slot of the pool eventually being occupied permanently since the vector is never freed. The solutions could be (1) freeing vector when the kfence object is freed or (2) allocating all vectors statically.

Since the memory consumption of object vectors is low, it is better to chose (2) to fix the issue and it is also can reduce overhead of vectors allocating in the future.

Link: https://lkml.kernel.org/r/20220328132843.16624-1-songmuchun@bytedance.com Fixes: d3fb45f370d9 ("mm, kfence: insert KFENCE hooks for SLAB") Signed-off-by: Muchun Song songmuchun@bytedance.com Reviewed-by: Marco Elver elver@google.com Reviewed-by: Roman Gushchin roman.gushchin@linux.dev Cc: Alexander Potapenko glider@google.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Xiongchun Duan duanxiongchun@bytedance.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org

diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 2f9fdfde1941..a203747ad2c0 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -566,6 +566,8 @@ static unsigned long kfence_init_pool(void) * enters __slab_free() slow-path. */ for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { + struct slab *slab = page_slab(&pages[i]); + if (!i || (i % 2)) continue;

@@ -573,7 +575,11 @@ static unsigned long kfence_init_pool(void) if (WARN_ON(compound_head(&pages[i]) != &pages[i])) return addr;

- __SetPageSlab(&pages[i]); + __folio_set_slab(slab_folio(slab)); +#ifdef CONFIG_MEMCG + slab->memcg_data = (unsigned long)&kfence_metadata[i / 2 - 1].objcg | + MEMCG_DATA_OBJCGS; +#endif }

/* @@ -1033,6 +1039,9 @@ void __kfence_free(void *addr) { struct kfence_metadata *meta = addr_to_metadata((unsigned long)addr);

+#ifdef CONFIG_MEMCG + KFENCE_WARN_ON(meta->objcg); +#endif /* * If the objects of the cache are SLAB_TYPESAFE_BY_RCU, defer freeing * the object, as the object page may be recycled for other-typed diff --git a/mm/kfence/kfence.h b/mm/kfence/kfence.h index 2a2d5de9d379..9a6c4b1b12a8 100644 --- a/mm/kfence/kfence.h +++ b/mm/kfence/kfence.h @@ -89,6 +89,9 @@ struct kfence_metadata { struct kfence_track free_track; /* For updating alloc_covered on frees. */ u32 alloc_stack_hash; +#ifdef CONFIG_MEMCG + struct obj_cgroup *objcg; +#endif };

extern struct kfence_metadata kfence_metadata[CONFIG_KFENCE_NUM_OBJECTS];