linux-kernel - Re: [PATCH] NTB: Fix UB/bug in ntb_mw_get

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Date:   Thu, 30 Nov 2017 15:07:52 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Serge Semin <fancer.lancer@...il.com>, jdmason@...zu.us,
        dave.jiang@...el.com, Allen.Hubbe@....com,
        Shyam-sundar.S-k@....com, Xiangliang.Yu@....com
Cc:     Sergey.Semin@...latforms.ru, linux-ntb@...glegroups.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] NTB: Fix UB/bug in ntb_mw_get_align()



On 30/11/17 02:39 PM, Serge Semin 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.
> 
> Signed-off-by: Serge Semin <fancer.lancer@...il.com>

Reviewed-by: Logan Gunthorpe <logang@...tatee.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,
>