Re: drivers/infiniband/sw/rxe/rxe_mr.c:106:9: warning: array subscript 0 is outside array bounds of 'struct sg_table[0]'

[Bob Pearson <rpearsonhpe@gmail.com>]

On 10/19/23 10:33, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   dd72f9c7e512da377074d47d990564959b772643
> commit: 592627ccbdff0ec6fff00fc761142a76db750dd4 RDMA/rxe: Replace rxe_map and rxe_phys_buf by xarray
> date:   9 months ago
> config: sparc-randconfig-c023-20211015 (https://download.01.org/0day-ci/archive/20231019/202310192300.lurP44yG-lkp@intel.com/config)
> compiler: sparc64-linux-gcc (GCC) 13.2.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231019/202310192300.lurP44yG-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202310192300.lurP44yG-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
>    drivers/infiniband/sw/rxe/rxe_mr.c: In function 'rxe_mr_fill_pages_from_sgt.constprop':
>>> drivers/infiniband/sw/rxe/rxe_mr.c:106:9: warning: array subscript 0 is outside array bounds of 'struct sg_table[0]' [-Warray-bounds=]
>      106 |         __sg_page_iter_start(&sg_iter, sgt->sgl, sgt->orig_nents, 0);
>          |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    cc1: note: source object is likely at address zero
>>> drivers/infiniband/sw/rxe/rxe_mr.c:106:9: warning: array subscript 0 is outside array bounds of 'struct sg_table[0]' [-Warray-bounds=]
>    cc1: note: source object is likely at address zero
> 
> 
> vim +106 drivers/infiniband/sw/rxe/rxe_mr.c
> 
>     98	
>     99	static int rxe_mr_fill_pages_from_sgt(struct rxe_mr *mr, struct sg_table *sgt)
>    100	{
>    101		XA_STATE(xas, &mr->page_list, 0);
>    102		struct sg_page_iter sg_iter;
>    103		struct page *page;
>    104		bool persistent = !!(mr->access & IB_ACCESS_FLUSH_PERSISTENT);
>    105	
>  > 106		__sg_page_iter_start(&sg_iter, sgt->sgl, sgt->orig_nents, 0);
>    107		if (!__sg_page_iter_next(&sg_iter))
>    108			return 0;
>    109	
>    110		do {
>    111			xas_lock(&xas);
>    112			while (true) {
>    113				page = sg_page_iter_page(&sg_iter);
>    114	
>    115				if (persistent && !is_pmem_page(page)) {
>    116					rxe_dbg_mr(mr, "Page can't be persistent\n");
>    117					xas_set_err(&xas, -EINVAL);
>    118					break;
>    119				}
>    120	
>    121				xas_store(&xas, page);
>    122				if (xas_error(&xas))
>    123					break;
>    124				xas_next(&xas);
>    125				if (!__sg_page_iter_next(&sg_iter))
>    126					break;
>    127			}
>    128			xas_unlock(&xas);
>    129		} while (xas_nomem(&xas, GFP_KERNEL));
>    130	
>    131		return xas_error(&xas);
>    132	}
>    133	
> 

Jason,

Can you make sense out of this? The marked line (was 106, now 101) seems completely innocuous.

Bob