Re: [PATCH v2 01/16] ovl: add permission hooks outside of do_splice_direct()

[Jan Kara <jack@suse.cz>]

On Wed 22-11-23 14:27:00, Amir Goldstein wrote:
> The main callers of do_splice_direct() also call rw_verify_area() for
> the entire range that is being copied, e.g. by vfs_copy_file_range()
> or do_sendfile() before calling do_splice_direct().
> 
> The only caller that does not have those checks for entire range is
> ovl_copy_up_file().  In preparation for removing the checks inside
> do_splice_direct(), add rw_verify_area() call in ovl_copy_up_file().
> 
> For extra safety, perform minimal sanity checks from rw_verify_area()
> for non negative offsets also in the copy up do_splice_direct() loop
> without calling the file permission hooks.
> 
> This is needed for fanotify "pre content" events.
> 
> Reviewed-by: Josef Bacik <josef@toxicpanda.com>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>

Looks good. Feel free to add:

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

								Honza


> ---
>  fs/overlayfs/copy_up.c | 26 +++++++++++++++++++++++++-
>  1 file changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index 4382881b0709..106f8643af3b 100644
> --- a/fs/overlayfs/copy_up.c
> +++ b/fs/overlayfs/copy_up.c
> @@ -230,6 +230,19 @@ static int ovl_copy_fileattr(struct inode *inode, const struct path *old,
>  	return ovl_real_fileattr_set(new, &newfa);
>  }
>  
> +static int ovl_verify_area(loff_t pos, loff_t pos2, loff_t len, loff_t totlen)
> +{
> +	loff_t tmp;
> +
> +	if (WARN_ON_ONCE(pos != pos2))
> +		return -EIO;
> +	if (WARN_ON_ONCE(pos < 0 || len < 0 || totlen < 0))
> +		return -EIO;
> +	if (WARN_ON_ONCE(check_add_overflow(pos, len, &tmp)))
> +		return -EIO;
> +	return 0;
> +}
> +
>  static int ovl_copy_up_file(struct ovl_fs *ofs, struct dentry *dentry,
>  			    struct file *new_file, loff_t len)
>  {
> @@ -244,13 +257,20 @@ static int ovl_copy_up_file(struct ovl_fs *ofs, struct dentry *dentry,
>  	int error = 0;
>  
>  	ovl_path_lowerdata(dentry, &datapath);
> -	if (WARN_ON(datapath.dentry == NULL))
> +	if (WARN_ON_ONCE(datapath.dentry == NULL) ||
> +	    WARN_ON_ONCE(len < 0))
>  		return -EIO;
>  
>  	old_file = ovl_path_open(&datapath, O_LARGEFILE | O_RDONLY);
>  	if (IS_ERR(old_file))
>  		return PTR_ERR(old_file);
>  
> +	error = rw_verify_area(READ, old_file, &old_pos, len);
> +	if (!error)
> +		error = rw_verify_area(WRITE, new_file, &new_pos, len);
> +	if (error)
> +		goto out_fput;
> +
>  	/* Try to use clone_file_range to clone up within the same fs */
>  	ovl_start_write(dentry);
>  	cloned = do_clone_file_range(old_file, 0, new_file, 0, len, 0);
> @@ -309,6 +329,10 @@ static int ovl_copy_up_file(struct ovl_fs *ofs, struct dentry *dentry,
>  			}
>  		}
>  
> +		error = ovl_verify_area(old_pos, new_pos, this_len, len);
> +		if (error)
> +			break;
> +
>  		ovl_start_write(dentry);
>  		bytes = do_splice_direct(old_file, &old_pos,
>  					 new_file, &new_pos,
> -- 
> 2.34.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR