[PATCH v2 01/16] slab: Remove __malloc attribute from realloc functions

From: Kees Cook <keescook@chromium.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: "Kees Cook" <keescook@chromium.org>,
	"Christoph Lameter" <cl@linux.com>,
	"Pekka Enberg" <penberg@kernel.org>,
	"David Rientjes" <rientjes@google.com>,
	"Joonsoo Kim" <iamjoonsoo.kim@lge.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Roman Gushchin" <roman.gushchin@linux.dev>,
	"Hyeonggon Yoo" <42.hyeyoo@gmail.com>,
	"Marco Elver" <elver@google.com>,
	linux-mm@kvack.org, "Ruhl, Michael J" <michael.j.ruhl@intel.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Eric Dumazet" <edumazet@google.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Paolo Abeni" <pabeni@redhat.com>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Nick Desaulniers" <ndesaulniers@google.com>,
	"Alex Elder" <elder@kernel.org>,
	"Josef Bacik" <josef@toxicpanda.com>,
	"David Sterba" <dsterba@suse.com>,
	"Sumit Semwal" <sumit.semwal@linaro.org>,
	"Christian König" <christian.koenig@amd.com>,
	"Jesse Brandeburg" <jesse.brandeburg@intel.com>,
	"Daniel Micay" <danielmicay@gmail.com>,
	"Yonghong Song" <yhs@fb.com>, "Miguel Ojeda" <ojeda@kernel.org>,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	linux-btrfs@vger.kernel.org, linux-media@vger.kernel.org,
	dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org,
	linux-fsdevel@vger.kernel.org, intel-wired-lan@lists.osuosl.org,
	dev@openvswitch.org, x86@kernel.org, llvm@lists.linux.dev,
	linux-hardening@vger.kernel.org
Subject: [PATCH v2 01/16] slab: Remove __malloc attribute from realloc functions
Date: Fri, 23 Sep 2022 13:28:07 -0700	[thread overview]
Message-ID: <20220923202822.2667581-2-keescook@chromium.org> (raw)
In-Reply-To: <20220923202822.2667581-1-keescook@chromium.org>

The __malloc attribute should not be applied to "realloc" functions, as
the returned pointer may alias the storage of the prior pointer. Instead
of splitting __malloc from __alloc_size, which would be a huge amount of
churn, just create __realloc_size for the few cases where it is needed.

Additionally removes the conditional test for __alloc_size__, which is
always defined now.

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: Vlastimil Babka <vbabka@suse.cz>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Marco Elver <elver@google.com>
Cc: linux-mm@kvack.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/compiler_types.h | 13 +++++--------
 include/linux/slab.h           | 12 ++++++------
 mm/slab_common.c               |  4 ++--
 3 files changed, 13 insertions(+), 16 deletions(-)

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 4f2a819fd60a..f141a6f6b9f6 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -271,15 +271,12 @@ struct ftrace_likely_data {
 
 /*
  * Any place that could be marked with the "alloc_size" attribute is also
- * a place to be marked with the "malloc" attribute. Do this as part of the
- * __alloc_size macro to avoid redundant attributes and to avoid missing a
- * __malloc marking.
+ * a place to be marked with the "malloc" attribute, except those that may
+ * be performing a _reallocation_, as that may alias the existing pointer.
+ * For these, use __realloc_size().
  */
-#ifdef __alloc_size__
-# define __alloc_size(x, ...)	__alloc_size__(x, ## __VA_ARGS__) __malloc
-#else
-# define __alloc_size(x, ...)	__malloc
-#endif
+#define __alloc_size(x, ...)	__alloc_size__(x, ## __VA_ARGS__) __malloc
+#define __realloc_size(x, ...)	__alloc_size__(x, ## __VA_ARGS__)
 
 #ifndef asm_volatile_goto
 #define asm_volatile_goto(x...) asm goto(x)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 0fefdf528e0d..41bd036e7551 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -184,7 +184,7 @@ int kmem_cache_shrink(struct kmem_cache *s);
 /*
  * Common kmalloc functions provided by all allocators
  */
-void * __must_check krealloc(const void *objp, size_t new_size, gfp_t flags) __alloc_size(2);
+void * __must_check krealloc(const void *objp, size_t new_size, gfp_t flags) __realloc_size(2);
 void kfree(const void *objp);
 void kfree_sensitive(const void *objp);
 size_t __ksize(const void *objp);
@@ -647,10 +647,10 @@ static inline __alloc_size(1, 2) void *kmalloc_array(size_t n, size_t size, gfp_
  * @new_size: new size of a single member of the array
  * @flags: the type of memory to allocate (see kmalloc)
  */
-static inline __alloc_size(2, 3) void * __must_check krealloc_array(void *p,
-								    size_t new_n,
-								    size_t new_size,
-								    gfp_t flags)
+static inline __realloc_size(2, 3) void * __must_check krealloc_array(void *p,
+								      size_t new_n,
+								      size_t new_size,
+								      gfp_t flags)
 {
 	size_t bytes;
 
@@ -774,7 +774,7 @@ static inline __alloc_size(1, 2) void *kvcalloc(size_t n, size_t size, gfp_t fla
 }
 
 extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
-		      __alloc_size(3);
+		      __realloc_size(3);
 extern void kvfree(const void *addr);
 extern void kvfree_sensitive(const void *addr, size_t len);
 
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 17996649cfe3..457671ace7eb 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1134,8 +1134,8 @@ module_init(slab_proc_init);
 
 #endif /* CONFIG_SLAB || CONFIG_SLUB_DEBUG */
 
-static __always_inline void *__do_krealloc(const void *p, size_t new_size,
-					   gfp_t flags)
+static __always_inline __realloc_size(2) void *
+__do_krealloc(const void *p, size_t new_size, gfp_t flags)
 {
 	void *ret;
 	size_t ks;
-- 
2.34.1

