linux-kernel - Re: [PATCH 0/6] slab: Provide full coverage for __alloc

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Message-Id: <63ced4a4-33b9-4c03-8d7a-987ceb1fc2c7@app.fastmail.com>
Date:   Tue, 29 Nov 2022 13:33:03 +0100
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Conor.Dooley" <conor.dooley@...rochip.com>,
        "Kees Cook" <keescook@...omium.org>
Cc:     "Vlastimil Babka" <vbabka@...e.cz>,
        "David Gow" <davidgow@...gle.com>,
        "Christoph Lameter" <cl@...ux.com>,
        "Pekka Enberg" <penberg@...nel.org>,
        "David Rientjes" <rientjes@...gle.com>,
        "Joonsoo Kim" <iamjoonsoo.kim@....com>,
        "Roman Gushchin" <roman.gushchin@...ux.dev>,
        "Hyeonggon Yoo" <42.hyeyoo@...il.com>,
        "Rasmus Villemoes" <rasmus.villemoes@...vas.dk>,
        "Guenter Roeck" <linux@...ck-us.net>,
        "Andy Shevchenko" <andriy.shevchenko@...el.com>,
        "Paolo Abeni" <pabeni@...hat.com>,
        "Geert Uytterhoeven" <geert@...ux-m68k.org>,
        "Nathan Chancellor" <nathan@...nel.org>,
        "Nick Desaulniers" <ndesaulniers@...gle.com>,
        "Tom Rix" <trix@...hat.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-hardening@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH 0/6] slab: Provide full coverage for __alloc_size attribute

On Tue, Nov 29, 2022, at 13:24, Conor Dooley wrote:
> On Tue, Nov 01, 2022 at 03:33:08PM -0700, Kees Cook wrote:
>> Hi,
>> 
>> This is a series to work around a deficiency in GCC (>=11) and Clang
>> (<16) where the __alloc_size attribute does not apply to inlines. :(
>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96503
>> 
>> This manifests as reduced overflow detection coverage for many allocation
>> sites under CONFIG_FORTIFY_SOURCE=y, where the allocation size was
>> not actually being propagated to __builtin_dynamic_object_size(). In
>> addition to working around the issue, expand use of __alloc_size (and
>> __realloc_size) to more places and provide KUnit tests to validate all
>> the covered allocator APIs.
>
> Hello Kees!
>
> It would appear that one of the macros you've added here is doing Bad
> Things^TM to allmodconfig on RISC-V since the 22nd:
>
> ../lib/fortify_kunit.c: In function 'alloc_size_kmalloc_const_test':
> ../lib/fortify_kunit.c:140:1: error: the frame size of 2384 bytes is 
> larger than 2048 bytes [-Werror=frame-larger-than=]
>   140 | }                                                               
>         \
>       | ^
> ../lib/fortify_kunit.c:209:1: note: in expansion of macro 
> 'DEFINE_ALLOC_SIZE_TEST_PAIR'
>   209 | DEFINE_ALLOC_SIZE_TEST_PAIR(kmalloc)
>       | ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
>
> CONFIG_GCC_VERSION=110100
> CONFIG_AS_VERSION=23700
> CONFIG_LD_VERSION=23700
>
> The report came out of my CI (which I should have passed on sooner) so
> I do not have anything other than stderr - I can get you anything else
> you'd like/need though if you LMK.

There is generally a conflict between kunit and the structleak
gcc plugin, I think the Makefile needs a line like

CFLAGS_fortify_kunit.o += $(DISABLE_STRUCTLEAK_PLUGIN)

      Arnd