linux-hardening - Re: [PATCH v2 6/7] percpu: Add __alloc_size attributes for better bounds checking

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Date:   Thu, 19 Aug 2021 22:11:15 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org, Daniel Micay <danielmicay@...il.com>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>, linux-mm@...ck.org,
        Joe Perches <joe@...ches.com>, Miguel Ojeda <ojeda@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Andy Whitcroft <apw@...onical.com>,
        Dwaipayan Ray <dwaipayanray1@...il.com>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        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: Re: [PATCH v2 6/7] percpu: Add __alloc_size attributes for better
 bounds checking

On Wed, 18 Aug 2021 14:40:20 -0700 Kees Cook <keescook@...omium.org> wrote:

> 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.
> 

Caught one, I assume:

In file included from ./include/linux/string.h:262,
                 from ./include/linux/bitmap.h:11,
                 from ./include/linux/cpumask.h:12,
                 from ./arch/x86/include/asm/cpumask.h:5,
                 from ./arch/x86/include/asm/msr.h:11,
                 from ./arch/x86/include/asm/processor.h:22,
                 from ./arch/x86/include/asm/cpufeature.h:5,
                 from ./arch/x86/include/asm/thread_info.h:53,
                 from ./include/linux/thread_info.h:60,
                 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/slab.h:15,
                 from drivers/misc/lkdtm/heap.c:7:
In function 'memset',
    inlined from 'lkdtm_VMALLOC_LINEAR_OVERFLOW' at drivers/misc/lkdtm/heap.c:27:2:
./include/linux/fortify-string.h:172:3: error: call to '__write_overflow' declared with attribute error: detected write beyond size of object passed as 1st parameter
  172 |   __write_overflow();
      |   ^~~~~~~~~~~~~~~~~~
make[3]: *** [drivers/misc/lkdtm/heap.o] Error 1
make[2]: *** [drivers/misc/lkdtm] Error 2
make[1]: *** [drivers/misc] Error 2
make: *** [drivers] Error 2

I want to get a kernel release out, so I'll hide
mm-vmalloc-add-__alloc_size-attributes-for-better-bounds-checking.patch
for now.