Re: [PATCH v2 03/15] NTB: Fix UB/bug in ntb_mw_get_align()

Jon Mason
2017-12-05T16:52:35Z

On Sun, Dec 3, 2017 at 2:17 PM, Serge Semin <fancer.lancer@gmail.com> wrote:
> Simple (1 << pidx) operation causes undefined behaviour when
> pidx >= 32. It must be casted to u64 to match the actual return
> value of ntb_link_is_up() method, so to have all the possible
> peer indexes covered and to get rid of undefined behaviour.
> Additionally there are special macros in "linux/bitops.h" to perform
> the bit-set-shift operations, so it's recommended to have them used
> for proper bit setting.

This looks good to me, but also seems like a bug fix. Please comment
on if this is not noticed.

Thanks,
Jon

>
> Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
> Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
> ---
> include/linux/ntb.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/ntb.h b/include/linux/ntb.h
> index c1646f2c6344..488e586fb76c 100644
> --- a/include/linux/ntb.h
> +++ b/include/linux/ntb.h
> @@ -764,7 +764,7 @@ static inline int ntb_mw_get_align(struct ntb_dev *ntb, int pidx, int widx,
> resource_size_t *size_align,
> resource_size_t *size_max)
> {
> - if (!(ntb_link_is_up(ntb, NULL, NULL) & (1 << pidx)))
> + if (!(ntb_link_is_up(ntb, NULL, NULL) & BIT_ULL(pidx)))
> return -ENOTCONN;
>
> return ntb->ops->mw_get_align(ntb, pidx, widx, addr_align, size_align,
> --
> 2.12.0
>