Re: [PATCH 2/4] mm/madvise: split out madvise input validity check

["Liam R. Howlett" <Liam.Howlett@oracle.com>]

* SeongJae Park <sj@kernel.org> [250206 01:15]:
> Split out the madvise parameters validation logic from do_madvise(), for
> easy reuse of the logic from a future change.
> 
> Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
> Signed-off-by: SeongJae Park <sj@kernel.org>

Reviewed-by: Liam R. Howlett <howlett@gmail.com>

> ---
>  mm/madvise.c | 32 ++++++++++++++++++++++----------
>  1 file changed, 22 insertions(+), 10 deletions(-)
> 
> diff --git a/mm/madvise.c b/mm/madvise.c
> index df5a87a1846a..efab2878be7c 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -1594,6 +1594,27 @@ static void madvise_unlock(struct mm_struct *mm, int behavior)
>  		mmap_read_unlock(mm);
>  }
>  
> +static bool is_valid_madvise(unsigned long start, size_t len_in, int behavior)
> +{
> +	size_t len;
> +
> +	if (!madvise_behavior_valid(behavior))
> +		return false;
> +
> +	if (!PAGE_ALIGNED(start))
> +		return false;
> +	len = PAGE_ALIGN(len_in);
> +
> +	/* Check to see whether len was rounded up from small -ve to zero */
> +	if (len_in && !len)
> +		return false;
> +
> +	if (start + len < start)
> +		return false;
> +
> +	return true;
> +}
> +
>  /*
>   * The madvise(2) system call.
>   *
> @@ -1673,20 +1694,11 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh
>  	size_t len;
>  	struct blk_plug plug;
>  
> -	if (!madvise_behavior_valid(behavior))
> +	if (!is_valid_madvise(start, len_in, behavior))
>  		return -EINVAL;
>  
> -	if (!PAGE_ALIGNED(start))
> -		return -EINVAL;
>  	len = PAGE_ALIGN(len_in);
> -
> -	/* Check to see whether len was rounded up from small -ve to zero */
> -	if (len_in && !len)
> -		return -EINVAL;
> -
>  	end = start + len;
> -	if (end < start)
> -		return -EINVAL;
>  
>  	if (end == start)
>  		return 0;
> -- 
> 2.39.5