linux-kernel - Re: [PATCH][next] fs: Annotate struct file_handle with __counted_by() and use struct

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Message-ID: <20240326085753.dh6fj7skdzddkdva@quack3>
Date: Tue, 26 Mar 2024 09:57:53 +0100
From: Jan Kara <jack@...e.cz>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	Chuck Lever <chuck.lever@...cle.com>,
	Jeff Layton <jlayton@...nel.org>,
	Amir Goldstein <amir73il@...il.com>, linux-fsdevel@...r.kernel.org,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] fs: Annotate struct file_handle with
 __counted_by() and use struct_size()

On Mon 25-03-24 19:34:01, Gustavo A. R. Silva wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
> array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> While there, use struct_size() helper, instead of the open-coded
> version.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/fhandle.c       | 8 ++++----
>  include/linux/fs.h | 2 +-
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/fhandle.c b/fs/fhandle.c
> index 57a12614addf..53ed54711cd2 100644
> --- a/fs/fhandle.c
> +++ b/fs/fhandle.c
> @@ -36,7 +36,7 @@ static long do_sys_name_to_handle(const struct path *path,
>  	if (f_handle.handle_bytes > MAX_HANDLE_SZ)
>  		return -EINVAL;
>  
> -	handle = kzalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
> +	handle = kzalloc(struct_size(handle, f_handle, f_handle.handle_bytes),
>  			 GFP_KERNEL);
>  	if (!handle)
>  		return -ENOMEM;
> @@ -71,7 +71,7 @@ static long do_sys_name_to_handle(const struct path *path,
>  	/* copy the mount id */
>  	if (put_user(real_mount(path->mnt)->mnt_id, mnt_id) ||
>  	    copy_to_user(ufh, handle,
> -			 sizeof(struct file_handle) + handle_bytes))
> +			 struct_size(handle, f_handle, handle_bytes)))
>  		retval = -EFAULT;
>  	kfree(handle);
>  	return retval;
> @@ -192,7 +192,7 @@ static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
>  		retval = -EINVAL;
>  		goto out_err;
>  	}
> -	handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
> +	handle = kmalloc(struct_size(handle, f_handle, f_handle.handle_bytes),
>  			 GFP_KERNEL);
>  	if (!handle) {
>  		retval = -ENOMEM;
> @@ -202,7 +202,7 @@ static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
>  	*handle = f_handle;
>  	if (copy_from_user(&handle->f_handle,
>  			   &ufh->f_handle,
> -			   f_handle.handle_bytes)) {
> +			   struct_size(ufh, f_handle, f_handle.handle_bytes))) {
>  		retval = -EFAULT;
>  		goto out_handle;
>  	}
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 034f0c918eea..1540e28d10d7 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1033,7 +1033,7 @@ struct file_handle {
>  	__u32 handle_bytes;
>  	int handle_type;
>  	/* file identifier */
> -	unsigned char f_handle[];
> +	unsigned char f_handle[] __counted_by(handle_bytes);
>  };
>  
>  static inline struct file *get_file(struct file *f)
> -- 
> 2.34.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR