From 9ed9cac1850a2a55674b4a17100c50b46f645921 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 23 Sep 2022 13:28:07 -0700 Subject: slab: Remove __malloc attribute from realloc functions 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. Thanks to Geert Uytterhoeven for reporting build failures with gcc-8 in earlier version which tried to remove the #ifdef. While the "alloc_size" attribute is available on all GCC versions, I forgot that it gets disabled explicitly by the kernel in GCC < 9.1 due to misbehaviors. Add a note to the compiler_attributes.h entry for it. Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Andrew Morton Cc: Vlastimil Babka Cc: Roman Gushchin Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Marco Elver Cc: linux-mm@kvack.org Signed-off-by: Kees Cook Signed-off-by: Vlastimil Babka --- include/linux/compiler_types.h | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'include/linux/compiler_types.h') diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 4f2a819fd60a..0717534f8364 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -271,14 +271,16 @@ 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 +# define __realloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) #else # define __alloc_size(x, ...) __malloc +# define __realloc_size(x, ...) #endif #ifndef asm_volatile_goto -- cgit v1.2.3-59-g8ed1b