Re: [PATCH v3] ARM: smp: add support for per-task stack canaries

[Russell King - ARM Linux <linux@armlinux.org.uk>]

On Sun, Dec 09, 2018 at 06:28:11PM +0800, kbuild test robot wrote:
> Hi Ard,
> 
> I love your patch! Perhaps something to improve:

Hi,

This looks to me like a false warning - how can a patch touching arch
code affect the result of lib/test_ubsan.c?  Please can you double-
check this result?

Thanks.

> 
> [auto build test WARNING on arm/for-next]
> [also build test WARNING on v4.20-rc5]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> 
> url:    https://github.com/0day-ci/linux/commits/Ard-Biesheuvel/ARM-smp-add-support-for-per-task-stack-canaries/20181209-033321
> base:   git://git.armlinux.org.uk/~rmk/linux-arm.git for-next
> config: arm-allmodconfig (attached as .config)
> compiler: arm-linux-gnueabi-gcc (Debian 7.2.0-11) 7.2.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # save the attached .config to linux build tree
>         GCC_VERSION=7.2.0 make.cross ARCH=arm 
> 
> All warnings (new ones prefixed by >>):
> 
>    lib/test_ubsan.c: In function 'test_ubsan_vla_bound_not_positive':
> >> lib/test_ubsan.c:48:2: warning: ISO C90 forbids variable length array 'buf' [-Wvla]
>      char buf[size];
>      ^~~~
>    lib/test_ubsan.c: In function 'test_ubsan_out_of_bounds':
> >> lib/test_ubsan.c:64:2: warning: ISO C90 forbids variable length array 'arr' [-Wvla]
>      volatile int arr[i];
>      ^~~~~~~~
> 
> vim +/buf +48 lib/test_ubsan.c
> 
> 854686f4 Jinbum Park 2018-04-10  44  
> 854686f4 Jinbum Park 2018-04-10  45  static void test_ubsan_vla_bound_not_positive(void)
> 854686f4 Jinbum Park 2018-04-10  46  {
> 854686f4 Jinbum Park 2018-04-10  47  	volatile int size = -1;
> 854686f4 Jinbum Park 2018-04-10 @48  	char buf[size];
> 854686f4 Jinbum Park 2018-04-10  49  
> 854686f4 Jinbum Park 2018-04-10  50  	(void)buf;
> 854686f4 Jinbum Park 2018-04-10  51  }
> 854686f4 Jinbum Park 2018-04-10  52  
> 854686f4 Jinbum Park 2018-04-10  53  static void test_ubsan_shift_out_of_bounds(void)
> 854686f4 Jinbum Park 2018-04-10  54  {
> 854686f4 Jinbum Park 2018-04-10  55  	volatile int val = -1;
> 854686f4 Jinbum Park 2018-04-10  56  	int val2 = 10;
> 854686f4 Jinbum Park 2018-04-10  57  
> 854686f4 Jinbum Park 2018-04-10  58  	val2 <<= val;
> 854686f4 Jinbum Park 2018-04-10  59  }
> 854686f4 Jinbum Park 2018-04-10  60  
> 854686f4 Jinbum Park 2018-04-10  61  static void test_ubsan_out_of_bounds(void)
> 854686f4 Jinbum Park 2018-04-10  62  {
> 854686f4 Jinbum Park 2018-04-10  63  	volatile int i = 4, j = 5;
> 854686f4 Jinbum Park 2018-04-10 @64  	volatile int arr[i];
> 854686f4 Jinbum Park 2018-04-10  65  
> 854686f4 Jinbum Park 2018-04-10  66  	arr[j] = i;
> 854686f4 Jinbum Park 2018-04-10  67  }
> 854686f4 Jinbum Park 2018-04-10  68  
> 
> :::::: The code at line 48 was first introduced by commit
> :::::: 854686f4edf483db1e0d26d972bdb8fb65c8bfaa lib: add testing module for UBSAN
> 
> :::::: TO: Jinbum Park <jinb.park7@gmail.com>
> :::::: CC: Linus Torvalds <torvalds@linux-foundation.org>
> 
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation



-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up