linux-kernel - Re: [PATCH v2] udf: Use kvzalloc() in udf_sb_alloc

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Date:   Thu, 27 Aug 2020 17:09:14 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Denis Efremov <efremov@...ux.com>, Jan Kara <jack@...e.com>
Cc:     linux-kernel@...r.kernel.org, Joe Perches <joe@...ches.com>
Subject: Re: [PATCH v2] udf: Use kvzalloc() in udf_sb_alloc_bitmap()



On 8/27/20 16:25, Denis Efremov wrote:
> Use kvzalloc() in udf_sb_alloc_bitmap() instead of open-coding it.
> Size computation wrapped in struct_size() macro to prevent potential
> integer overflows.
> 
> Signed-off-by: Denis Efremov <efremov@...ux.com>
> ---

Please, comment here what changed in v2, vn... e.g.:

Changes in v2:
 - Use struct_size() helper.


>  fs/udf/super.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/udf/super.c b/fs/udf/super.c
> index 1c42f544096d..bdf51bea54f3 100644
> --- a/fs/udf/super.c
> +++ b/fs/udf/super.c
> @@ -1010,14 +1010,9 @@ static struct udf_bitmap *udf_sb_alloc_bitmap(struct super_block *sb, u32 index)
>  	int size;
>  
>  	nr_groups = udf_compute_nr_groups(sb, index);
> -	size = sizeof(struct udf_bitmap) +
> -		(sizeof(struct buffer_head *) * nr_groups);
> -
> -	if (size <= PAGE_SIZE)
> -		bitmap = kzalloc(size, GFP_KERNEL);
> -	else
> -		bitmap = vzalloc(size); /* TODO: get rid of vzalloc */
> +	size = struct_size(bitmap, s_block_bitmap, nr_groups);
>  
> +	bitmap = kvzalloc(size, GFP_KERNEL);

Why not this:

bitmap = kvzalloc(struct_size(bitmap, s_block_bitmap, nr_groups),
		  GFP_KERNEL);

and you can also get rid of _size_ entirely.

Thanks
--
Gustavo

>  	if (!bitmap)
>  		return NULL;
>  
>