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Date:   Tue, 30 Aug 2022 14:49:03 -0700
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Subject: [RFC PATCH 14/30] mm: prevent slabobj_ext allocations for slabobj_ext
 and kmem_cache objects
From:   Suren Baghdasaryan <surenb@google.com>
To:     akpm@linux-foundation.org
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Precedence: bulk

Use __GFP_NO_OBJ_EXT to prevent recursions when allocating slabobj_ext
objects. Also prevent slabobj_ext allocations for kmem_cache objects.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 mm/memcontrol.c | 2 ++
 mm/slab.h       | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3f407ef2f3f1..dabb451dc364 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2809,6 +2809,8 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
 	void *vec;
 
 	gfp &= ~OBJCGS_CLEAR_MASK;
+	/* Prevent recursive extension vector allocation */
+	gfp |= __GFP_NO_OBJ_EXT;
 	vec = kcalloc_node(objects, sizeof(struct slabobj_ext), gfp,
 			   slab_nid(slab));
 	if (!vec)
diff --git a/mm/slab.h b/mm/slab.h
index c767ce3f0fe2..d93b22b8bbe2 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -475,6 +475,12 @@ static inline void prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags,
 	if (is_kmem_only_obj_ext())
 		return;
 
+	if (s->flags & SLAB_NO_OBJ_EXT)
+		return;
+
+	if (flags & __GFP_NO_OBJ_EXT)
+		return;
+
 	slab = virt_to_slab(p);
 	if (!slab_obj_exts(slab))
 		WARN(alloc_slab_obj_exts(slab, s, flags, false),
-- 
2.37.2.672.g94769d06f0-goog