linux-hardening - Re: [PATCH v3 4/8] slab: Add __alloc_size attributes for better bounds checking

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Date:   Tue, 5 Oct 2021 18:47:17 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andy Whitcroft <apw@...onical.com>,
        Dennis Zhou <dennis@...nel.org>,
        Dwaipayan Ray <dwaipayanray1@...il.com>,
        Joe Perches <joe@...ches.com>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Tejun Heo <tj@...nel.org>,
        Daniel Micay <danielmicay@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.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: Re: [PATCH v3 4/8] slab: Add __alloc_size attributes for better
 bounds checking

On Thu, 30 Sep 2021 15:27:00 -0700 Kees Cook <keescook@...omium.org> wrote:

> 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.

x86_64 allmodconfig:

In file included from ./arch/x86/include/asm/preempt.h:7,
                 from ./include/linux/preempt.h:78,
                 from ./include/linux/spinlock.h:55,
                 from ./include/linux/mmzone.h:8,
                 from ./include/linux/gfp.h:6,
                 from ./include/linux/mm.h:10,
                 from ./include/linux/mman.h:5,
                 from lib/test_kasan_module.c:10:
In function 'check_copy_size',
    inlined from 'copy_user_test' at ./include/linux/uaccess.h:191:6:
./include/linux/thread_info.h:213:4: error: call to '__bad_copy_to' declared with attribute error: copy destination size is too small
  213 |    __bad_copy_to();
      |    ^~~~~~~~~~~~~~~
In function 'check_copy_size',
    inlined from 'copy_user_test' at ./include/linux/uaccess.h:199:6:
./include/linux/thread_info.h:211:4: error: call to '__bad_copy_from' declared with attribute error: copy source size is too small
  211 |    __bad_copy_from();
      |    ^~~~~~~~~~~~~~~~~
make[1]: *** [lib/test_kasan_module.o] Error 1
make: *** [lib] Error 2