linux-kernel - Re: [PATCH] btrfs: Refactor allocation size calculation in kzalloc()

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Message-ID: <76fa5e79-c7e8-4637-bf51-c0e6f4e04f51@gmx.com>
Date: Tue, 30 Sep 2025 18:49:55 +0930
From: Qu Wenruo <quwenruo.btrfs@....com>
To: Mehdi Ben Hadj Khelifa <mehdi.benhadjkhelifa@...il.com>, clm@...com,
 dsterba@...e.com
Cc: linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
 skhan@...uxfoundation.org, david.hunter.linux@...il.com,
 linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] btrfs: Refactor allocation size calculation in kzalloc()



在 2025/9/30 18:44, Mehdi Ben Hadj Khelifa 写道:
> Wrap allocation size calculation in size_add() and size_mul() to avoid
> any potential overflow.
> 
> Signed-off-by: Mehdi Ben Hadj Khelifa <mehdi.benhadjkhelifa@...il.com>
> ---
>   fs/btrfs/volumes.c | 11 +++++------
>   1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index c6e3efd6f602..3f1f19b28aac 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -6076,12 +6076,11 @@ struct btrfs_io_context *alloc_btrfs_io_context(struct btrfs_fs_info *fs_info,
>   {
>   	struct btrfs_io_context *bioc;
>   
> -	bioc = kzalloc(
> -		 /* The size of btrfs_io_context */
> -		sizeof(struct btrfs_io_context) +
> -		/* Plus the variable array for the stripes */
> -		sizeof(struct btrfs_io_stripe) * (total_stripes),
> -		GFP_NOFS);
> +	/* The size of btrfs_io_context */
> +	/* Plus the variable array for the stripes */
> +	bioc = kzalloc(size_add(sizeof(struct btrfs_io_context),

Please use struct_size() instead.

And if you're using struct_size() there iwll be no need for any comments.
> +				size_mul(sizeof(struct btrfs_io_stripe),
> +						total_stripes)), GFP_NOFS);
>   
>   	if (!bioc)
>   		return NULL;