linux-hardening - [PATCH v3 8/8] percpu: Add __alloc_size attributes for better bounds checking

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Date:   Thu, 30 Sep 2021 15:27:04 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>, Dennis Zhou <dennis@...nel.org>,
        Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>,
        Andy Whitcroft <apw@...onical.com>,
        David Rientjes <rientjes@...gle.com>,
        Dwaipayan Ray <dwaipayanray1@...il.com>,
        Joe Perches <joe@...ches.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Pekka Enberg <penberg@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Daniel Micay <danielmicay@...il.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        clang-built-linux@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH v3 8/8] percpu: Add __alloc_size attributes for better bounds checking

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

Note that due to the implementation of the percpu API, this is unlikely
to ever actually provide compile-time checking beyond very simple non-SMP
builds. But, since they are technically allocators, mark them as such.

Cc: Dennis Zhou <dennis@...nel.org>
Cc: Tejun Heo <tj@...nel.org>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Andy Whitcroft <apw@...onical.com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Dwaipayan Ray <dwaipayanray1@...il.com>
Cc: Joe Perches <joe@...ches.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Lukas Bulwahn <lukas.bulwahn@...il.com>
Cc: Miguel Ojeda <ojeda@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Pekka Enberg <penberg@...nel.org>
Cc: Vlastimil Babka <vbabka@...e.cz>
Co-developed-by: Daniel Micay <danielmicay@...il.com>
Signed-off-by: Daniel Micay <danielmicay@...il.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/linux/percpu.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index 5e76af742c80..98a9371133f8 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -123,7 +123,7 @@ extern int __init pcpu_page_first_chunk(size_t reserved_size,
 				pcpu_fc_populate_pte_fn_t populate_pte_fn);
 #endif
 
-extern void __percpu *__alloc_reserved_percpu(size_t size, size_t align);
+extern void __percpu *__alloc_reserved_percpu(size_t size, size_t align) __alloc_size(1);
 extern bool __is_kernel_percpu_address(unsigned long addr, unsigned long *can_addr);
 extern bool is_kernel_percpu_address(unsigned long addr);
 
@@ -131,8 +131,8 @@ extern bool is_kernel_percpu_address(unsigned long addr);
 extern void __init setup_per_cpu_areas(void);
 #endif
 
-extern void __percpu *__alloc_percpu_gfp(size_t size, size_t align, gfp_t gfp);
-extern void __percpu *__alloc_percpu(size_t size, size_t align);
+extern void __percpu *__alloc_percpu_gfp(size_t size, size_t align, gfp_t gfp) __alloc_size(1);
+extern void __percpu *__alloc_percpu(size_t size, size_t align) __alloc_size(1);
 extern void free_percpu(void __percpu *__pdata);
 extern phys_addr_t per_cpu_ptr_to_phys(void *addr);
 
-- 
2.30.2