LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Kees Cook <keescook@chromium.org>
To: Dennis Zhou <dennis@kernel.org>
Cc: linux-kernel@vger.kernel.org,
	Daniel Micay <danielmicay@gmail.com>, Tejun Heo <tj@kernel.org>,
	Christoph Lameter <cl@linux.com>,
	linux-mm@kvack.org, Joe Perches <joe@perches.com>,
	Miguel Ojeda <ojeda@kernel.org>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Andy Whitcroft <apw@canonical.com>,
	Dwaipayan Ray <dwaipayanray1@gmail.com>,
	Lukas Bulwahn <lukas.bulwahn@gmail.com>,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Michal Marek <michal.lkml@markovi.net>,
	clang-built-linux@googlegroups.com, linux-kbuild@vger.kernel.org,
	linux-hardening@vger.kernel.org
Subject: Re: [PATCH v2 6/7] percpu: Add __alloc_size attributes for better bounds checking
Date: Wed, 18 Aug 2021 20:36:50 -0700	[thread overview]
Message-ID: <202108182018.6DA03EA818@keescook> (raw)
In-Reply-To: <YR2pE9V1P0xmBWUo@fedora>

On Wed, Aug 18, 2021 at 08:42:59PM -0400, Dennis Zhou wrote:
> On Wed, Aug 18, 2021 at 02:40:20PM -0700, Kees Cook 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.
> 
> Can you elaborate a little bit for me how this works for percpu? In any
> case that's not uniprocessor, any modification is done through address
> accessors and not on the returned percpu pointer. Is the metadata kept
> by gcc/clang able to transpire the percpu pointer accessors?

That's an excellent point. :P I haven't tested it through the accessors,
but I guess it's possible that this is only useful for UP, and even
then, only where the access is very close to the "allocation", maybe
like:

char __percpu *test_buf;

	char *buf;
	test_var = __alloc_percpu(16, __alignof__(char));
	buf = per_cpu_ptr(test_buf, get_cpu());
	...
	buf[20] = '!';

-Kees

> 
> Thanks,
> Dennis
> 
> > 
> > Co-developed-by: Daniel Micay <danielmicay@gmail.com>
> > Signed-off-by: Daniel Micay <danielmicay@gmail.com>
> > Cc: Dennis Zhou <dennis@kernel.org>
> > Cc: Tejun Heo <tj@kernel.org>
> > Cc: Christoph Lameter <cl@linux.com>
> > Cc: linux-mm@kvack.org
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> >  include/linux/percpu.h | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/include/linux/percpu.h b/include/linux/percpu.h
> > index 5e76af742c80..119f41815b32 100644
> > --- a/include/linux/percpu.h
> > +++ b/include/linux/percpu.h
> > @@ -123,6 +123,7 @@ extern int __init pcpu_page_first_chunk(size_t reserved_size,
> >  				pcpu_fc_populate_pte_fn_t populate_pte_fn);
> >  #endif
> >  
> > +__alloc_size(1)
> >  extern void __percpu *__alloc_reserved_percpu(size_t size, size_t align);
> >  extern bool __is_kernel_percpu_address(unsigned long addr, unsigned long *can_addr);
> >  extern bool is_kernel_percpu_address(unsigned long addr);
> > @@ -131,7 +132,9 @@ extern bool is_kernel_percpu_address(unsigned long addr);
> >  extern void __init setup_per_cpu_areas(void);
> >  #endif
> >  
> > +__alloc_size(1)
> >  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);
> >  extern void free_percpu(void __percpu *__pdata);
> >  extern phys_addr_t per_cpu_ptr_to_phys(void *addr);
> > -- 
> > 2.30.2
> > 

-- 
Kees Cook

  reply	other threads:[~2021-08-19  3:37 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18 21:40 [PATCH v2 0/7] Add __alloc_size() " Kees Cook
2021-08-18 21:40 ` [PATCH v2 1/7] Compiler Attributes: " Kees Cook
2021-08-18 21:51   ` Nathan Chancellor
2021-08-18 23:19   ` Andrew Morton
2021-08-19  7:06     ` Kees Cook
2021-08-19  0:04   ` Miguel Ojeda
2021-08-18 21:40 ` [PATCH v2 2/7] checkpatch: Add __alloc_size() to known $Attribute Kees Cook
2021-08-18 21:40 ` [PATCH v2 3/7] slab: Clean up function declarations Kees Cook
2021-08-18 21:40 ` [PATCH v2 4/7] slab: Add __alloc_size attributes for better bounds checking Kees Cook
2021-08-19  8:27   ` Rasmus Villemoes
2021-08-25 21:31   ` Nick Desaulniers
2021-09-22 22:41     ` Kees Cook
2021-08-18 21:40 ` [PATCH v2 5/7] mm/page_alloc: " Kees Cook
2021-08-18 21:40 ` [PATCH v2 6/7] percpu: " Kees Cook
2021-08-19  0:42   ` Dennis Zhou
2021-08-19  3:36     ` Kees Cook [this message]
2021-08-19 14:12       ` Dennis Zhou
2021-08-20  5:11   ` Andrew Morton
2021-08-20  5:27     ` Kees Cook
2021-08-18 21:40 ` [PATCH v2 7/7] mm/vmalloc: " Kees Cook

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=202108182018.6DA03EA818@keescook \
    --to=keescook@chromium.org \
    --cc=akpm@linux-foundation.org \
    --cc=apw@canonical.com \
    --cc=cl@linux.com \
    --cc=clang-built-linux@googlegroups.com \
    --cc=danielmicay@gmail.com \
    --cc=dennis@kernel.org \
    --cc=dwaipayanray1@gmail.com \
    --cc=iamjoonsoo.kim@lge.com \
    --cc=joe@perches.com \
    --cc=linux-hardening@vger.kernel.org \
    --cc=linux-kbuild@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=lukas.bulwahn@gmail.com \
    --cc=masahiroy@kernel.org \
    --cc=michal.lkml@markovi.net \
    --cc=nathan@kernel.org \
    --cc=ndesaulniers@google.com \
    --cc=ojeda@kernel.org \
    --cc=penberg@kernel.org \
    --cc=rientjes@google.com \
    --cc=tj@kernel.org \
    --cc=vbabka@suse.cz \
    --subject='Re: [PATCH v2 6/7] percpu: Add __alloc_size attributes for better bounds checking' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).