2024-02-21 19:45:45

by Suren Baghdasaryan

Subject: [PATCH v4 09/36] mm/slab: introduce SLAB_NO_OBJ_EXT to avoid obj_ext creation

Slab extension objects can't be allocated before slab infrastructure is
initialized. Some caches, like kmem_cache and kmem_cache_node, are created
before slab infrastructure is initialized. Objects from these caches can't
have extension objects. Introduce SLAB_NO_OBJ_EXT slab flag to mark these
caches and avoid creating extensions for objects allocated from these
slabs.

Signed-off-by: Suren Baghdasaryan <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
---
include/linux/slab.h | 6 ++++++
mm/slub.c | 5 +++--
2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index b5f5ee8308d0..58794043ab5b 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -28,6 +28,12 @@
*/
/* DEBUG: Perform (expensive) checks on alloc/free */
#define SLAB_CONSISTENCY_CHECKS ((slab_flags_t __force)0x00000100U)
+/* Slab created using create_boot_cache */
+#ifdef CONFIG_SLAB_OBJ_EXT
+#define SLAB_NO_OBJ_EXT ((slab_flags_t __force)0x00000200U)
+#else
+#define SLAB_NO_OBJ_EXT 0
+#endif
/* DEBUG: Red zone objs in a cache */
#define SLAB_RED_ZONE ((slab_flags_t __force)0x00000400U)
/* DEBUG: Poison objects */
diff --git a/mm/slub.c b/mm/slub.c
index ca803b2949fc..5dc7beda6c0d 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5697,7 +5697,8 @@ void __init kmem_cache_init(void)
node_set(node, slab_nodes);

create_boot_cache(kmem_cache_node, "kmem_cache_node",
- sizeof(struct kmem_cache_node), SLAB_HWCACHE_ALIGN, 0, 0);
+ sizeof(struct kmem_cache_node),
+ SLAB_HWCACHE_ALIGN | SLAB_NO_OBJ_EXT, 0, 0);

hotplug_memory_notifier(slab_memory_callback, SLAB_CALLBACK_PRI);

@@ -5707,7 +5708,7 @@ void __init kmem_cache_init(void)
create_boot_cache(kmem_cache, "kmem_cache",
offsetof(struct kmem_cache, node) +
nr_node_ids * sizeof(struct kmem_cache_node *),
- SLAB_HWCACHE_ALIGN, 0, 0);
+ SLAB_HWCACHE_ALIGN | SLAB_NO_OBJ_EXT, 0, 0);

kmem_cache = bootstrap(&boot_kmem_cache);
kmem_cache_node = bootstrap(&boot_kmem_cache_node);
--
2.44.0.rc0.258.g7320e95886-goog

2024-02-22 00:10:46

by Pasha Tatashin

Subject: Re: [PATCH v4 09/36] mm/slab: introduce SLAB_NO_OBJ_EXT to avoid obj_ext creation

On Wed, Feb 21, 2024 at 2:41 PM Suren Baghdasaryan <[email protected]> wrote:
>
> Slab extension objects can't be allocated before slab infrastructure is
> initialized. Some caches, like kmem_cache and kmem_cache_node, are created
> before slab infrastructure is initialized. Objects from these caches can't
> have extension objects. Introduce SLAB_NO_OBJ_EXT slab flag to mark these
> caches and avoid creating extensions for objects allocated from these
> slabs.
>
> Signed-off-by: Suren Baghdasaryan <[email protected]>
> Reviewed-by: Kees Cook <[email protected]>

Reviewed-by: Pasha Tatashin <[email protected]>

2024-02-26 16:53:34

by Vlastimil Babka

Subject: Re: [PATCH v4 09/36] mm/slab: introduce SLAB_NO_OBJ_EXT to avoid obj_ext creation

On 2/21/24 20:40, Suren Baghdasaryan wrote:
> Slab extension objects can't be allocated before slab infrastructure is
> initialized. Some caches, like kmem_cache and kmem_cache_node, are created
> before slab infrastructure is initialized. Objects from these caches can't
> have extension objects. Introduce SLAB_NO_OBJ_EXT slab flag to mark these
> caches and avoid creating extensions for objects allocated from these
> slabs.
>
> Signed-off-by: Suren Baghdasaryan <[email protected]>
> Reviewed-by: Kees Cook <[email protected]>

Reviewed-by: Vlastimil Babka <[email protected]>