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Date:   Tue, 24 Oct 2023 06:46:07 -0700
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Subject: [PATCH v2 10/39] 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/slab.h        | 6 ++++++
 mm/slab_common.c | 2 ++
 2 files changed, 8 insertions(+)

diff --git a/mm/slab.h b/mm/slab.h
index 5a47125469f1..187acc593397 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -489,6 +489,12 @@ prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)
 	if (!need_slab_obj_ext())
 		return NULL;
 
+	if (s->flags & SLAB_NO_OBJ_EXT)
+		return NULL;
+
+	if (flags & __GFP_NO_OBJ_EXT)
+		return NULL;
+
 	slab = virt_to_slab(p);
 	if (!slab_obj_exts(slab) &&
 	    WARN(alloc_slab_obj_exts(slab, s, flags, false),
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 2b42a9d2c11c..446f406d2703 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -222,6 +222,8 @@ 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)
-- 
2.42.0.758.gaed0368e0e-goog