Re: [PATCH v4 5/6] cifs: Use kstrndup for cifs_sb->mountdata

[Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Wed, 6 Apr 2011 16:26:44 +0200
Sean Finney <seanius-ADwgVSpYHhHR7s880joybQ@public.gmane.org> wrote:

> A relatively minor nit, but also clarified the "consensus" from the
> preceding comments that it is in fact better to try for the kstrdup
> early and cleanup while cleaning up is still a simple thing to do.
> 
> Reviewed-By: Steve French <smfrench-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Signed-off-by: Sean Finney <seanius-ADwgVSpYHhHR7s880joybQ@public.gmane.org>
> ---
>  fs/cifs/cifsfs.c |   18 +++++++-----------
>  1 files changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index fb6a2ad..cf8a610 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -134,24 +134,20 @@ cifs_read_super(struct super_block *sb, void *data,
>  	cifs_sb->bdi.ra_pages = default_backing_dev_info.ra_pages;
>  
>  #ifdef CONFIG_CIFS_DFS_UPCALL
> -	/* copy mount params to sb for use in submounts */
> -	/* BB: should we move this after the mount so we
> -	 * do not have to do the copy on failed mounts?
> -	 * BB: May be it is better to do simple copy before
> -	 * complex operation (mount), and in case of fail
> -	 * just exit instead of doing mount and attempting
> -	 * undo it if this copy fails?*/
> +	/*
> +	 * Copy mount params to sb for use in submounts. Better to do
> +	 * the copy here and deal with the error before cleanup gets
> +	 * complicated post-mount.
> +	 */
>  	if (data) {
> -		int len = strlen(data);
> -		cifs_sb->mountdata = kzalloc(len + 1, GFP_KERNEL);
> +		cifs_sb->mountdata = kstrndup(data, PAGE_CACHE_SIZE,
> +					      GFP_KERNEL);
>  		if (cifs_sb->mountdata == NULL) {
>  			bdi_destroy(&cifs_sb->bdi);
>  			kfree(sb->s_fs_info);
>  			sb->s_fs_info = NULL;
>  			return -ENOMEM;
>  		}
> -		strncpy(cifs_sb->mountdata, data, len + 1);
> -		cifs_sb->mountdata[len] = '\0';
>  	}
>  #endif
>  

I was wrong before, and we should be using PAGE_SIZE here instead of
PAGE_CACHE_SIZE. On all arches that I know of those are equivalent
currently, but that might not be the case in the future. It might not
hurt to change that in these patches though if you're respinning them
anyway.

Either way, you can add my:

Reviewed-by: Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>