Re: [linux-next:master 12105/12116] include/linux/thread_info.h:213:4: error: call to '__bad_copy_to' declared with attribute error: copy destination size is too small

From: Kees Cook <keescook@chromium.org>
To: kernel test robot <lkp@intel.com>
Cc: kbuild-all@lists.01.org,
	Linux Memory Management List <linux-mm@kvack.org>,
	Daniel Micay <danielmicay@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [linux-next:master 12105/12116] include/linux/thread_info.h:213:4: error: call to '__bad_copy_to' declared with attribute error: copy destination size is too small
Date: Thu, 9 Sep 2021 08:53:56 -0700	[thread overview]
Message-ID: <202109090853.369D71E1@keescook> (raw)
In-Reply-To: <202109090843.9E28C97@keescook>

On Thu, Sep 09, 2021 at 08:45:56AM -0700, Kees Cook wrote:
> On Thu, Sep 09, 2021 at 11:49:55AM +0800, kernel test robot wrote:
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> > head:   999569d59a0aa2509ae4a67ecc266c1134e37e7b
> > commit: f5b1a5d922d3199e0637349239b43aed6c7656b9 [12105/12116] mm/vmalloc: add __alloc_size attributes for better bounds checking
> > config: i386-randconfig-a002-20200329 (attached as .config)
> > compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
> > reproduce (this is a W=1 build):
> >         # https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=f5b1a5d922d3199e0637349239b43aed6c7656b9
> >         git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
> >         git fetch --no-tags linux-next master
> >         git checkout f5b1a5d922d3199e0637349239b43aed6c7656b9
> >         # save the attached .config to linux build tree
> >         mkdir build_dir
> >         make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash drivers/rapidio/devices/
> > 
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@intel.com>
> > 
> > All errors (new ones prefixed by >>):
> > 
> >    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/mm_types.h:9,
> >                     from include/linux/buildid.h:5,
> >                     from include/linux/module.h:14,
> >                     from drivers/rapidio/devices/rio_mport_cdev.c:13:
> >    In function 'check_copy_size',
> >        inlined from 'copy_from_user' at include/linux/uaccess.h:191:6,
> >        inlined from 'rio_mport_transfer_ioctl' at drivers/rapidio/devices/rio_mport_cdev.c:983:6:
> > >> 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();
> >          |    ^~~~~~~~~~~~~~~
> 
> 
>         transfer = vmalloc(array_size(sizeof(*transfer), transaction.count));
>         if (!transfer)
>                 return -ENOMEM;
> 
>         if (unlikely(copy_from_user(transfer,
>                                     (void __user *)(uintptr_t)transaction.block,
>                                     array_size(sizeof(*transfer), transaction.count)))) {
> 
> Uhhhmm... allocation size and copy size are identical...
> 
>       array_size(sizeof(*transfer), transaction.count)
> 	array_size(sizeof(*transfer), transaction.count)

This appears to be an optimization(?) bug in GCC 9.3. This warning
(correctly) does not appear in later versions.

-- 
Kees Cook