mm: introduce __GFP_NO_OBJ_EXT flag to selectively prevent slabobj_ext creation

Introduce __GFP_NO_OBJ_EXT flag in order to prevent recursive allocations
when allocating slabobj_ext on a slab.

Link: https://lkml.kernel.org/r/20240321163705.3067592-8-surenb@google.comSigned-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Kees Cook <keescook@chromium.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alex Gaynor <alex.gaynor@gmail.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Andreas Hindborg <a.hindborg@samsung.com>
Cc: Benno Lossin <benno.lossin@proton.me>
Cc: "Björn Roy Baron" <bjorn3_gh@protonmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Gary Guo <gary@garyguo.net>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/gfp_types.h

@@ -54,6 +54,9 @@ enum {
 #endif
 #ifdef CONFIG_LOCKDEP
 	___GFP_NOLOCKDEP_BIT,
+#endif
+#ifdef CONFIG_SLAB_OBJ_EXT
+	___GFP_NO_OBJ_EXT_BIT,
 #endif
 	___GFP_LAST_BIT
 };
@@ -95,6 +98,11 @@ enum {
 #else
 #define ___GFP_NOLOCKDEP	0
 #endif
+#ifdef CONFIG_SLAB_OBJ_EXT
+#define ___GFP_NO_OBJ_EXT       BIT(___GFP_NO_OBJ_EXT_BIT)
+#else
+#define ___GFP_NO_OBJ_EXT       0
+#endif
 
 /*
  * Physical address zone modifiers (see linux/mmzone.h - low four bits)
@@ -135,12 +143,15 @@ enum {
  * node with no fallbacks or placement policy enforcements.
  *
  * %__GFP_ACCOUNT causes the allocation to be accounted to kmemcg.
+ *
+ * %__GFP_NO_OBJ_EXT causes slab allocation to have no object extension.
  */
 #define __GFP_RECLAIMABLE ((__force gfp_t)___GFP_RECLAIMABLE)
 #define __GFP_WRITE	((__force gfp_t)___GFP_WRITE)
 #define __GFP_HARDWALL   ((__force gfp_t)___GFP_HARDWALL)
 #define __GFP_THISNODE	((__force gfp_t)___GFP_THISNODE)
 #define __GFP_ACCOUNT	((__force gfp_t)___GFP_ACCOUNT)
+#define __GFP_NO_OBJ_EXT   ((__force gfp_t)___GFP_NO_OBJ_EXT)
 
 /**
  * DOC: Watermark modifiers

mm/slub.c

@@ -1889,6 +1889,8 @@ static 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)