mm/vmalloc.c:2782:58: warning: operation on 'data->idx' may be undefined

mm/vmalloc.c:2782:58: warning: operation on 'data->idx' may be undefined

[kernel test robot]

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tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   d4439a1189f93d0ac1eaf0197db8e6b3e197d5c7
commit: 9a8797722e4239242d0cb4cc4baa805df6ac979e Drivers: hv: vmbus: Initialize VMbus ring buffer for Isolation VM
date:   8 days ago
config: arm64-randconfig-r022-20211105 (attached as .config)
compiler: aarch64-linux-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9a8797722e4239242d0cb4cc4baa805df6ac979e
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 9a8797722e4239242d0cb4cc4baa805df6ac979e
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=arm64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   In file included from arch/arm64/include/asm/kasan.h:10,
                    from arch/arm64/include/asm/processor.h:39,
                    from include/asm-generic/qrwlock.h:14,
                    from ./arch/arm64/include/generated/asm/qrwlock.h:1,
                    from arch/arm64/include/asm/spinlock.h:9,
                    from include/linux/spinlock.h:94,
                    from include/linux/vmalloc.h:5,
                    from mm/vmalloc.c:11:
   mm/vmalloc.c: In function 'vmap_pfn_apply':
>> mm/vmalloc.c:2782:58: warning: operation on 'data->idx' may be undefined [-Wsequence-point]
    2782 |         *pte = pte_mkspecial(pfn_pte(data->pfns[data->idx++], data->prot));
         |                                                 ~~~~~~~~~^~
   arch/arm64/include/asm/pgtable-types.h:25:37: note: in definition of macro '__pte'
      25 | #define __pte(x)        ((pte_t) { (x) } )
         |                                     ^
   arch/arm64/include/asm/pgtable.h:80:15: note: in expansion of macro '__phys_to_pte_val'
      80 |         __pte(__phys_to_pte_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
         |               ^~~~~~~~~~~~~~~~~
   mm/vmalloc.c:2782:30: note: in expansion of macro 'pfn_pte'
    2782 |         *pte = pte_mkspecial(pfn_pte(data->pfns[data->idx++], data->prot));
         |                              ^~~~~~~


vim +2782 mm/vmalloc.c

3e9a9e256b1e1e Christoph Hellwig 2020-10-17  2775  
3e9a9e256b1e1e Christoph Hellwig 2020-10-17  2776  static int vmap_pfn_apply(pte_t *pte, unsigned long addr, void *private)
3e9a9e256b1e1e Christoph Hellwig 2020-10-17  2777  {
3e9a9e256b1e1e Christoph Hellwig 2020-10-17  2778  	struct vmap_pfn_data *data = private;
3e9a9e256b1e1e Christoph Hellwig 2020-10-17  2779  
3e9a9e256b1e1e Christoph Hellwig 2020-10-17  2780  	if (WARN_ON_ONCE(pfn_valid(data->pfns[data->idx])))
3e9a9e256b1e1e Christoph Hellwig 2020-10-17  2781  		return -EINVAL;
3e9a9e256b1e1e Christoph Hellwig 2020-10-17 @2782  	*pte = pte_mkspecial(pfn_pte(data->pfns[data->idx++], data->prot));
3e9a9e256b1e1e Christoph Hellwig 2020-10-17  2783  	return 0;
3e9a9e256b1e1e Christoph Hellwig 2020-10-17  2784  }
3e9a9e256b1e1e Christoph Hellwig 2020-10-17  2785  

:::::: The code at line 2782 was first introduced by commit
:::::: 3e9a9e256b1e1e6e8f19faf76fa9c37578ae35ee mm: add a vmap_pfn function

:::::: TO: Christoph Hellwig <hch@lst.de>
:::::: CC: Linus Torvalds <torvalds@linux-foundation.org>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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