linux-kernel - Re: [PATCH RFC v2 2/4] mm/mempolicy: remove redundant check in get

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Date:   Tue, 31 Oct 2017 09:55:35 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Yisheng Xie <xieyisheng1@...wei.com>, akpm@...ux-foundation.org,
        mhocko@...e.com, mingo@...nel.org, rientjes@...gle.com,
        n-horiguchi@...jp.nec.com, salls@...ucsb.edu
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        tanxiaojun@...wei.com, linux-api@...r.kernel.org
Subject: Re: [PATCH RFC v2 2/4] mm/mempolicy: remove redundant check in
 get_nodes

On 10/27/2017 12:14 PM, Yisheng Xie wrote:
> We have already checked whether maxnode is a page worth of bits, by:
>     maxnode > PAGE_SIZE*BITS_PER_BYTE
> 
> So no need to check it once more.
> 
> Signed-off-by: Yisheng Xie <xieyisheng1@...wei.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  mm/mempolicy.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 613e9d0..3b51bb3 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -1280,8 +1280,6 @@ static int get_nodes(nodemask_t *nodes, const unsigned long __user *nmask,
>  	/* When the user specified more nodes than supported just check
>  	   if the non supported part is all zero. */
>  	if (nlongs > BITS_TO_LONGS(MAX_NUMNODES)) {
> -		if (nlongs > PAGE_SIZE/sizeof(long))
> -			return -EINVAL;
>  		for (k = BITS_TO_LONGS(MAX_NUMNODES); k < nlongs; k++) {
>  			unsigned long t;
>  			if (get_user(t, nmask + k))
>