linux-kernel - Re: [PATCH] ext4: Annotate struct ext4_xattr_inode_array with __counted

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Message-ID: <66A83FFC.7020802@huawei.com>
Date: Tue, 30 Jul 2024 09:21:00 +0800
From: "yebin (H)" <yebin10@...wei.com>
To: Thorsten Blum <thorsten.blum@...lux.com>, <tytso@....edu>,
	<adilger.kernel@...ger.ca>, <kees@...nel.org>, <gustavoars@...nel.org>
CC: <linux-ext4@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-hardening@...r.kernel.org>
Subject: Re: [PATCH] ext4: Annotate struct ext4_xattr_inode_array with
 __counted_by()



On 2024/7/29 19:04, Thorsten Blum wrote:
> Add the __counted_by compiler attribute to the flexible array member
> inodes to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
> CONFIG_FORTIFY_SOURCE.
>
> Remove the now obsolete comment on the count field.
>
> Signed-off-by: Thorsten Blum <thorsten.blum@...lux.com>
> ---
>   fs/ext4/xattr.h | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h
> index bd97c4aa8177..e14fb19dc912 100644
> --- a/fs/ext4/xattr.h
> +++ b/fs/ext4/xattr.h
> @@ -130,8 +130,8 @@ struct ext4_xattr_ibody_find {
>   };
>   
>   struct ext4_xattr_inode_array {
> -	unsigned int count;		/* # of used items in the array */
> -	struct inode *inodes[];
> +	unsigned int count;
As the comment says, 'count' is the number of items in the array that 
have been used,
not the total number of items in the array. So I think this check was 
added incorrectly.
> +	struct inode *inodes[] __counted_by(count);
>   };
>   
>   extern const struct xattr_handler ext4_xattr_user_handler;