linux-kernel - Re: [PATCH v4] memory_hotplug: Add a bounds check to __add

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Date:   Thu, 26 Sep 2019 23:35:05 +0800
From:   kbuild test robot <lkp@...el.com>
To:     Alastair D'Silva <alastair@....ibm.com>
Cc:     kbuild-all@...org, alastair@...ilva.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...e.com>,
        David Hildenbrand <david@...hat.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Dan Williams <dan.j.williams@...el.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] memory_hotplug: Add a bounds check to __add_pages

Hi Alastair,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[cannot apply to v5.3 next-20190925]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Alastair-D-Silva/memory_hotplug-Add-a-bounds-check-to-__add_pages/20190926-094437
config: i386-randconfig-g004-201938 (attached as .config)
compiler: gcc-7 (Debian 7.4.0-13) 7.4.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@...el.com>

All warnings (new ones prefixed by >>):

   mm/memory_hotplug.c: In function 'check_hotplug_memory_addressable':
>> mm/memory_hotplug.c:286:15: warning: right shift count >= width of type [-Wshift-count-overflow]
     if (max_addr >> MAX_PHYSMEM_BITS) {
                  ^~
   In file included from arch/x86/include/asm/bug.h:83:0,
                    from include/linux/bug.h:5,
                    from include/linux/mmdebug.h:5,
                    from include/linux/mm.h:9,
                    from mm/memory_hotplug.c:9:
>> mm/memory_hotplug.c:290:13: warning: left shift count >= width of type [-Wshift-count-overflow]
           (1ul << (MAX_PHYSMEM_BITS + 1)) - 1);
                ^
   include/asm-generic/bug.h:112:21: note: in definition of macro '__WARN_printf_taint'
     do { __warn_printk(arg); __WARN_TAINT(taint); } while (0)
                        ^~~
   include/asm-generic/bug.h:135:3: note: in expansion of macro '__WARN_printf'
      __WARN_printf(format);     \
      ^~~~~~~~~~~~~
>> mm/memory_hotplug.c:287:3: note: in expansion of macro 'WARN'
      WARN(1,
      ^~~~

vim +286 mm/memory_hotplug.c

   280	
   281	static int check_hotplug_memory_addressable(unsigned long pfn,
   282						    unsigned long nr_pages)
   283	{
   284		unsigned long max_addr = ((pfn + nr_pages) << PAGE_SHIFT) - 1;
   285	
 > 286		if (max_addr >> MAX_PHYSMEM_BITS) {
 > 287			WARN(1,
   288			     "Hotplugged memory exceeds maximum addressable address, range=%#lx-%#lx, maximum=%#lx\n",
   289			     pfn << PAGE_SHIFT, max_addr,
 > 290			     (1ul << (MAX_PHYSMEM_BITS + 1)) - 1);
   291			return -E2BIG;
   292		}
   293	
   294		return 0;
   295	}
   296	

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