Date:   Tue, 17 Aug 2021 22:08:38 -0700
From:   Kees Cook <keescook@...omium.org>
To:     linux-kernel@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Daniel Micay <danielmicay@...il.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
        Miguel Ojeda <ojeda@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        clang-built-linux@...glegroups.com, linux-kbuild@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH 2/5] slab: Add __alloc_size attributes for better bounds checking

As already done in GrapheneOS, add the __alloc_size attribute for
regular kmalloc interfaces, to provide additional hinting for better
bounds checking, assisting CONFIG_FORTIFY_SOURCE and other compiler
optimizations.

Co-developed-by: Daniel Micay <danielmicay@...il.com>
Signed-off-by: Daniel Micay <danielmicay@...il.com>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Pekka Enberg <penberg@...nel.org>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: linux-mm@...ck.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/linux/slab.h | 50 +++++++++++++++++++++++++++-----------------
 1 file changed, 31 insertions(+), 19 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index c0d46b6fa12a..b2181c176999 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -181,7 +181,7 @@ int kmem_cache_shrink(struct kmem_cache *);
 /*
  * Common kmalloc functions provided by all allocators
  */
-void * __must_check krealloc(const void *, size_t, gfp_t);
+void * __must_check krealloc(const void *, size_t, gfp_t) __alloc_size(2);
 void kfree(const void *);
 void kfree_sensitive(const void *);
 size_t __ksize(const void *);
@@ -425,7 +425,7 @@ static __always_inline unsigned int __kmalloc_index(size_t size,
 #define kmalloc_index(s) __kmalloc_index(s, true)
 #endif /* !CONFIG_SLOB */
 
-void *__kmalloc(size_t size, gfp_t flags) __assume_kmalloc_alignment __malloc;
+void *__kmalloc(size_t size, gfp_t flags) __alloc_size(1) __assume_kmalloc_alignment __malloc;
 void *kmem_cache_alloc(struct kmem_cache *, gfp_t flags) __assume_slab_alignment __malloc;
 void kmem_cache_free(struct kmem_cache *, void *);
 
@@ -449,7 +449,8 @@ static __always_inline void kfree_bulk(size_t size, void **p)
 }
 
 #ifdef CONFIG_NUMA
-void *__kmalloc_node(size_t size, gfp_t flags, int node) __assume_kmalloc_alignment __malloc;
+void *__kmalloc_node(size_t size, gfp_t flags, int node) __alloc_size(1)
+							 __assume_kmalloc_alignment __malloc;
 void *kmem_cache_alloc_node(struct kmem_cache *, gfp_t flags, int node) __assume_slab_alignment __malloc;
 #else
 static __always_inline void *__kmalloc_node(size_t size, gfp_t flags, int node)
@@ -574,7 +575,7 @@ static __always_inline void *kmalloc_large(size_t size, gfp_t flags)
  *	Try really hard to succeed the allocation but fail
  *	eventually.
  */
-static __always_inline void *kmalloc(size_t size, gfp_t flags)
+static __always_inline __alloc_size(1) void *kmalloc(size_t size, gfp_t flags)
 {
 	if (__builtin_constant_p(size)) {
 #ifndef CONFIG_SLOB
@@ -596,7 +597,8 @@ static __always_inline void *kmalloc(size_t size, gfp_t flags)
 	return __kmalloc(size, flags);
 }
 
-static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
+static __always_inline __alloc_size(1) void *
+kmalloc_node(size_t size, gfp_t flags, int node)
 {
 #ifndef CONFIG_SLOB
 	if (__builtin_constant_p(size) &&
@@ -620,7 +622,8 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
  * @size: element size.
  * @flags: the type of memory to allocate (see kmalloc).
  */
-static inline void *kmalloc_array(size_t n, size_t size, gfp_t flags)
+static inline __alloc_size(1, 2) void *
+kmalloc_array(size_t n, size_t size, gfp_t flags)
 {
 	size_t bytes;
 
@@ -638,7 +641,7 @@ static inline void *kmalloc_array(size_t n, size_t size, gfp_t flags)
  * @new_size: new size of a single member of the array
  * @flags: the type of memory to allocate (see kmalloc)
  */
-static __must_check inline void *
+static __must_check inline __alloc_size(2, 3) void *
 krealloc_array(void *p, size_t new_n, size_t new_size, gfp_t flags)
 {
 	size_t bytes;
@@ -655,7 +658,8 @@ krealloc_array(void *p, size_t new_n, size_t new_size, gfp_t flags)
  * @size: element size.
  * @flags: the type of memory to allocate (see kmalloc).
  */
-static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
+static inline __alloc_size(1, 2) void *
+kcalloc(size_t n, size_t size, gfp_t flags)
 {
 	return kmalloc_array(n, size, flags | __GFP_ZERO);
 }
@@ -684,7 +688,8 @@ static inline void *kmalloc_array_node(size_t n, size_t size, gfp_t flags,
 	return __kmalloc_node(bytes, flags, node);
 }
 
-static inline void *kcalloc_node(size_t n, size_t size, gfp_t flags, int node)
+static inline __alloc_size(1, 2) void *
+kcalloc_node(size_t n, size_t size, gfp_t flags, int node)
 {
 	return kmalloc_array_node(n, size, flags | __GFP_ZERO, node);
 }
@@ -716,7 +721,8 @@ static inline void *kmem_cache_zalloc(struct kmem_cache *k, gfp_t flags)
  * @size: how many bytes of memory are required.
  * @flags: the type of memory to allocate (see kmalloc).
  */
-static inline void *kzalloc(size_t size, gfp_t flags)
+static inline __alloc_size(1) void *
+kzalloc(size_t size, gfp_t flags)
 {
 	return kmalloc(size, flags | __GFP_ZERO);
 }
@@ -727,26 +733,31 @@ static inline void *kzalloc(size_t size, gfp_t flags)
  * @flags: the type of memory to allocate (see kmalloc).
  * @node: memory node from which to allocate
  */
-static inline void *kzalloc_node(size_t size, gfp_t flags, int node)
+static inline __alloc_size(1) void *
+kzalloc_node(size_t size, gfp_t flags, int node)
 {
 	return kmalloc_node(size, flags | __GFP_ZERO, node);
 }
 
-extern void *kvmalloc_node(size_t size, gfp_t flags, int node);
-static inline void *kvmalloc(size_t size, gfp_t flags)
+extern __alloc_size(1) void *
+kvmalloc_node(size_t size, gfp_t flags, int node);
+static inline __alloc_size(1) void *kvmalloc(size_t size, gfp_t flags)
 {
 	return kvmalloc_node(size, flags, NUMA_NO_NODE);
 }
-static inline void *kvzalloc_node(size_t size, gfp_t flags, int node)
+static inline __alloc_size(1) void *
+kvzalloc_node(size_t size, gfp_t flags, int node)
 {
 	return kvmalloc_node(size, flags | __GFP_ZERO, node);
 }
-static inline void *kvzalloc(size_t size, gfp_t flags)
+static inline __alloc_size(1) void *
+kvzalloc(size_t size, gfp_t flags)
 {
 	return kvmalloc(size, flags | __GFP_ZERO);
 }
 
-static inline void *kvmalloc_array(size_t n, size_t size, gfp_t flags)
+static inline __alloc_size(1, 2) void *
+kvmalloc_array(size_t n, size_t size, gfp_t flags)
 {
 	size_t bytes;
 
@@ -756,13 +767,14 @@ static inline void *kvmalloc_array(size_t n, size_t size, gfp_t flags)
 	return kvmalloc(bytes, flags);
 }
 
-static inline void *kvcalloc(size_t n, size_t size, gfp_t flags)
+static inline __alloc_size(1, 2) void *
+kvcalloc(size_t n, size_t size, gfp_t flags)
 {
 	return kvmalloc_array(n, size, flags | __GFP_ZERO);
 }
 
-extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize,
-		gfp_t flags);
+extern __alloc_size(3) void *
+kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags);
 extern void kvfree(const void *addr);
 extern void kvfree_sensitive(const void *addr, size_t len);
 
-- 
2.30.2

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