Re: [PATCH v3] sunrpc: Fix error checking for d_hash_and_lookup()

[Jeff Layton <jlayton@kernel.org>]

On Wed, 2024-08-28 at 12:43 +0800, Yan Zhen wrote:
> The d_hash_and_lookup() function returns either an error pointer or NULL.
> 
> It might be more appropriate to check error using IS_ERR_OR_NULL().
> 
> Fixes: 4b9a445e3eeb ("sunrpc: create a new dummy pipe for gssd to hold open")
> Signed-off-by: Yan Zhen <yanzhen@vivo.com>
> ---
> 
> Changes in v3:
> - Rewrite the "fixes".
> - Using ERR_CAST(gssd_dentry) instead of ERR_PTR(-ENOENT).
> 
>  net/sunrpc/rpc_pipe.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
> index 910a5d850d04..13e905f34359 100644
> --- a/net/sunrpc/rpc_pipe.c
> +++ b/net/sunrpc/rpc_pipe.c
> @@ -1306,8 +1306,8 @@ rpc_gssd_dummy_populate(struct dentry *root, struct rpc_pipe *pipe_data)
>  
>  	/* We should never get this far if "gssd" doesn't exist */
>  	gssd_dentry = d_hash_and_lookup(root, &q);
> -	if (!gssd_dentry)
> -		return ERR_PTR(-ENOENT);
> +	if (IS_ERR_OR_NULL(gssd_dentry))
> +		return ERR_CAST(gssd_dentry);

If you get back a NULL, then ERR_CAST will just make this return a NULL
pointer.

>  
>  	ret = rpc_populate(gssd_dentry, gssd_dummy_clnt_dir, 0, 1, NULL);
>  	if (ret) {
> @@ -1318,7 +1318,7 @@ rpc_gssd_dummy_populate(struct dentry *root, struct rpc_pipe *pipe_data)
>  	q.name = gssd_dummy_clnt_dir[0].name;
>  	q.len = strlen(gssd_dummy_clnt_dir[0].name);
>  	clnt_dentry = d_hash_and_lookup(gssd_dentry, &q);
> -	if (!clnt_dentry) {
> +	if (IS_ERR_OR_NULL(clnt_dentry)) {
>  		__rpc_depopulate(gssd_dentry, gssd_dummy_clnt_dir, 0, 1);
>  		pipe_dentry = ERR_PTR(-ENOENT);
>  		goto out;

...you probably also want to make this return the error from
d_hash_and_lookup as well when there is one.
-- 
Jeff Layton <jlayton@kernel.org>