linux-kernel - Re: [PATCH v2 3/3] nfsd: Propagate some error code returned by memdup

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Date:   Thu, 01 Sep 2022 07:25:59 -0400
From:   Jeff Layton <jlayton@...nel.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Chuck Lever <chuck.lever@...cle.com>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Dan Carpenter <dan.carpenter@...cle.com>,
        linux-nfs@...r.kernel.org
Subject: Re: [PATCH v2 3/3] nfsd: Propagate some error code returned by
 memdup_user()

On Thu, 2022-09-01 at 07:27 +0200, Christophe JAILLET wrote:
> Propagate the error code returned by memdup_user() instead of a hard coded
> -EFAULT.
> 
> Suggested-by: Dan Carpenter <dan.carpenter@...cle.com>
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
> This patch is speculative. The whole call chains have not been checked to
> see if there was no path explicitly expecting a -EFAULT.
> ---
>  fs/nfsd/nfs4recover.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
> index 2968cf604e3b..78b8cd9651d5 100644
> --- a/fs/nfsd/nfs4recover.c
> +++ b/fs/nfsd/nfs4recover.c
> @@ -808,7 +808,7 @@ __cld_pipe_inprogress_downcall(const struct cld_msg_v2 __user *cmsg,
>  				return -EFAULT;
>  			name.data = memdup_user(&ci->cc_name.cn_id, namelen);
>  			if (IS_ERR(name.data))
> -				return -EFAULT;
> +				return PTR_ERR(name.data);
>  			name.len = namelen;
>  			get_user(princhashlen, &ci->cc_princhash.cp_len);
>  			if (princhashlen > 0) {
> @@ -817,7 +817,7 @@ __cld_pipe_inprogress_downcall(const struct cld_msg_v2 __user *cmsg,
>  						princhashlen);
>  				if (IS_ERR(princhash.data)) {
>  					kfree(name.data);
> -					return -EFAULT;
> +					return PTR_ERR(princhash.data);
>  				}
>  				princhash.len = princhashlen;
>  			} else
> @@ -830,7 +830,7 @@ __cld_pipe_inprogress_downcall(const struct cld_msg_v2 __user *cmsg,
>  				return -EFAULT;
>  			name.data = memdup_user(&cnm->cn_id, namelen);
>  			if (IS_ERR(name.data))
> -				return -EFAULT;
> +				return PTR_ERR(name.data);
>  			name.len = namelen;
>  		}
>  		if (name.len > 5 && memcmp(name.data, "hash:", 5) == 0) {

I *think* this error gets propagated to userland on a write to
rpc_pipefs, and the callers already handle a variety of errors. This
looks reasonable to me. 

Reviewed-by: Jeff Layton <jlayton@...nel.org>