linux-kernel - Re: [PATCH 2/4] mm/shmem: return -EINVAL for addr not PAGE

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Message-ID: <d5f4c444-032d-81f6-c7b8-6e1627aaf7f7@redhat.com>
Date:   Wed, 1 Jun 2022 15:37:55 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Chen Wandun <chenwandun@...wei.com>, hughd@...gle.com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] mm/shmem: return -EINVAL for addr not PAGE_SIZE
 aligned

On 01.06.22 14:44, Chen Wandun wrote:
> If addr is not PAGE_SIZE aligned, return -EINVAL directly.

Why is this one to be treated in a special way compared to all of the
other related checks?

> Besides, use macro offset_in_page to check addr is not
> PAGE_SIZE aligned case.

Using offset_in_page() LGTM.

> 
> Signed-off-by: Chen Wandun <chenwandun@...wei.com>
> ---
>  mm/shmem.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 80c361c3d82c..1136dd7da9e5 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2143,8 +2143,8 @@ unsigned long shmem_get_unmapped_area(struct file *file,
>  		return addr;
>  	if (IS_ERR_VALUE(addr))
>  		return addr;
> -	if (addr & ~PAGE_MASK)
> -		return addr;
> +	if (offset_in_page(addr))
> +		return -EINVAL;
>  	if (addr > TASK_SIZE - len)
>  		return addr;
>  
> @@ -2197,7 +2197,7 @@ unsigned long shmem_get_unmapped_area(struct file *file,
>  	inflated_addr = get_area(NULL, uaddr, inflated_len, 0, flags);
>  	if (IS_ERR_VALUE(inflated_addr))
>  		return addr;
> -	if (inflated_addr & ~PAGE_MASK)
> +	if (offset_in_page(inflated_addr))
>  		return addr;
>  
>  	inflated_offset = inflated_addr & (HPAGE_PMD_SIZE-1);


-- 
Thanks,

David / dhildenb