[PATCH 3/6] slab: Provide functional __alloc_size() hints to kmalloc_trace*()

[Kees Cook <keescook@chromium.org>]

Since GCC cannot apply the __alloc_size attributes to inlines[1], all
allocator inlines need to explicitly call into extern functions that
contain a size argument. Provide these wrappers that end up just
ignoring the size argument for the actual allocation.

This allows CONFIG_FORTIFY_SOURCE=y to see all various dynamic allocation
sizes under GCC 12+ and all supported Clang versions.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96503

Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: linux-mm@kvack.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/slab.h |  8 ++++++--
 mm/slab_common.c     | 14 ++++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 970e9504949e..051d86ca31a8 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -442,6 +442,8 @@ static_assert(PAGE_SHIFT <= 20);
 
 void *__kmalloc(size_t size, gfp_t flags) __assume_kmalloc_alignment __alloc_size(1);
 void *kmem_cache_alloc(struct kmem_cache *s, gfp_t flags) __assume_slab_alignment __malloc;
+void *kmem_cache_alloc_sized(struct kmem_cache *s, gfp_t flags, size_t size)
+			     __assume_slab_alignment __alloc_size(3);
 void *kmem_cache_alloc_lru(struct kmem_cache *s, struct list_lru *lru,
 			   gfp_t gfpflags) __assume_slab_alignment __malloc;
 void kmem_cache_free(struct kmem_cache *s, void *objp);
@@ -469,6 +471,8 @@ void *__kmalloc_node(size_t size, gfp_t flags, int node) __assume_kmalloc_alignm
 							 __alloc_size(1);
 void *kmem_cache_alloc_node(struct kmem_cache *s, gfp_t flags, int node) __assume_slab_alignment
 									 __malloc;
+void *kmem_cache_alloc_node_sized(struct kmem_cache *s, gfp_t flags, int node, size_t size)
+				  __assume_slab_alignment __alloc_size(4);
 
 #ifdef CONFIG_TRACING
 void *kmalloc_trace(struct kmem_cache *s, gfp_t flags, size_t size)
@@ -482,7 +486,7 @@ void *kmalloc_node_trace(struct kmem_cache *s, gfp_t gfpflags,
 static __always_inline __alloc_size(3)
 void *kmalloc_trace(struct kmem_cache *s, gfp_t flags, size_t size)
 {
-	void *ret = kmem_cache_alloc(s, flags);
+	void *ret = kmem_cache_alloc_sized(s, flags, size);
 
 	ret = kasan_kmalloc(s, ret, size, flags);
 	return ret;
@@ -492,7 +496,7 @@ static __always_inline __alloc_size(4)
 void *kmalloc_node_trace(struct kmem_cache *s, gfp_t gfpflags,
 			 int node, size_t size)
 {
-	void *ret = kmem_cache_alloc_node(s, gfpflags, node);
+	void *ret = kmem_cache_alloc_node_sized(s, gfpflags, node, size);
 
 	ret = kasan_kmalloc(s, ret, size, gfpflags);
 	return ret;
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 33b1886b06eb..5fa547539a6a 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1457,6 +1457,20 @@ size_t ksize(const void *objp)
 }
 EXPORT_SYMBOL(ksize);
 
+/* Wrapper so __alloc_size() can see the actual allocation size. */
+void *kmem_cache_alloc_sized(struct kmem_cache *s, gfp_t flags, size_t size)
+{
+	return kmem_cache_alloc(s, flags);
+}
+EXPORT_SYMBOL(kmem_cache_alloc_sized);
+
+/* Wrapper so __alloc_size() can see the actual allocation size. */
+void *kmem_cache_alloc_node_sized(struct kmem_cache *s, gfp_t flags, int node, size_t size)
+{
+	return kmem_cache_alloc_node(s, flags, node);
+}
+EXPORT_SYMBOL(kmem_cache_alloc_node_sized);
+
 /* Tracepoints definitions. */
 EXPORT_TRACEPOINT_SYMBOL(kmalloc);
 EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);
-- 
2.34.1