[viro-vfs:work.iov_iter_get_pages 24/33] lib/iov_iter.c:1295 iter_xarray_get_pages() warn: unsigned 'count' is never less than zero.

[viro-vfs:work.iov_iter_get_pages 24/33] lib/iov_iter.c:1295 iter_xarray_get_pages() warn: unsigned 'count' is never less than zero.

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git work.iov_iter_get_pages
head:   fe8e2809c7db0ec65403b31b50906f3f481a9b10
commit: e64d637d648390e4ac0643747ae174c3be15f243 [24/33] iov_iter: saner helper for page array allocation
config: mips-randconfig-m031-20220619 (https://download.01.org/0day-ci/archive/20220619/202206192306.POJg04ej-lkp@intel.com/config)
compiler: mips-linux-gcc (GCC) 11.3.0

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

smatch warnings:
lib/iov_iter.c:1295 iter_xarray_get_pages() warn: unsigned 'count' is never less than zero.

vim +/count +1295 lib/iov_iter.c

  1280	
  1281	static ssize_t iter_xarray_get_pages(struct iov_iter *i,
  1282					     struct page ***pages, size_t maxsize,
  1283					     unsigned maxpages, size_t *_start_offset)
  1284	{
  1285		unsigned nr, offset;
  1286		pgoff_t index, count;
  1287		loff_t pos;
  1288	
  1289		pos = i->xarray_start + i->iov_offset;
  1290		index = pos >> PAGE_SHIFT;
  1291		offset = pos & ~PAGE_MASK;
  1292		*_start_offset = offset;
  1293	
  1294		count = want_pages_array(pages, maxsize, offset, maxpages);
> 1295		if (count < 0)
  1296			return count;
  1297		nr = iter_xarray_populate_pages(*pages, i->xarray, index, count);
  1298		if (nr == 0)
  1299			return 0;
  1300	
  1301		return min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
  1302	}
  1303	

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

Re: [viro-vfs:work.iov_iter_get_pages 24/33] lib/iov_iter.c:1295 iter_xarray_get_pages() warn: unsigned 'count' is never less than zero.

[Al Viro]

On Sun, Jun 19, 2022 at 11:40:37PM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git work.iov_iter_get_pages
> head:   fe8e2809c7db0ec65403b31b50906f3f481a9b10
> commit: e64d637d648390e4ac0643747ae174c3be15f243 [24/33] iov_iter: saner helper for page array allocation
> config: mips-randconfig-m031-20220619 (https://download.01.org/0day-ci/archive/20220619/202206192306.POJg04ej-lkp@intel.com/config)
> compiler: mips-linux-gcc (GCC) 11.3.0
> 
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@intel.com>
> 
> smatch warnings:
> lib/iov_iter.c:1295 iter_xarray_get_pages() warn: unsigned 'count' is never less than zero.

Joy...  Should've been int all along, obviously (pgoff_t for number of array
elements?)

Re: [viro-vfs:work.iov_iter_get_pages 24/33] lib/iov_iter.c:1295 iter_xarray_get_pages() warn: unsigned 'count' is never less than zero.

[Matthew Wilcox]

On Sun, Jun 19, 2022 at 04:48:54PM +0100, Al Viro wrote:
> On Sun, Jun 19, 2022 at 11:40:37PM +0800, kernel test robot wrote:
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git work.iov_iter_get_pages
> > head:   fe8e2809c7db0ec65403b31b50906f3f481a9b10
> > commit: e64d637d648390e4ac0643747ae174c3be15f243 [24/33] iov_iter: saner helper for page array allocation
> > config: mips-randconfig-m031-20220619 (https://download.01.org/0day-ci/archive/20220619/202206192306.POJg04ej-lkp@intel.com/config)
> > compiler: mips-linux-gcc (GCC) 11.3.0
> > 
> > If you fix the issue, kindly add following tag where applicable
> > Reported-by: kernel test robot <lkp@intel.com>
> > 
> > smatch warnings:
> > lib/iov_iter.c:1295 iter_xarray_get_pages() warn: unsigned 'count' is never less than zero.
> 
> Joy...  Should've been int all along, obviously (pgoff_t for number of array
> elements?)

I've been using 'long' for that just because I don't want the drama of
"we need to support 16GB pages" to have anything to do with me.

Re: [viro-vfs:work.iov_iter_get_pages 24/33] lib/iov_iter.c:1295 iter_xarray_get_pages() warn: unsigned 'count' is never less than zero.

[Al Viro]

On Sun, Jun 19, 2022 at 04:54:57PM +0100, Matthew Wilcox wrote:
> On Sun, Jun 19, 2022 at 04:48:54PM +0100, Al Viro wrote:
> > On Sun, Jun 19, 2022 at 11:40:37PM +0800, kernel test robot wrote:
> > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git work.iov_iter_get_pages
> > > head:   fe8e2809c7db0ec65403b31b50906f3f481a9b10
> > > commit: e64d637d648390e4ac0643747ae174c3be15f243 [24/33] iov_iter: saner helper for page array allocation
> > > config: mips-randconfig-m031-20220619 (https://download.01.org/0day-ci/archive/20220619/202206192306.POJg04ej-lkp@intel.com/config)
> > > compiler: mips-linux-gcc (GCC) 11.3.0
> > > 
> > > If you fix the issue, kindly add following tag where applicable
> > > Reported-by: kernel test robot <lkp@intel.com>
> > > 
> > > smatch warnings:
> > > lib/iov_iter.c:1295 iter_xarray_get_pages() warn: unsigned 'count' is never less than zero.
> > 
> > Joy...  Should've been int all along, obviously (pgoff_t for number of array
> > elements?)
> 
> I've been using 'long' for that just because I don't want the drama of
> "we need to support 16GB pages" to have anything to do with me.

That's "kvmalloc a flat array with that many pointers to pages in it and
and pin those suckers"...