Re: [PATCH] nfsd4: fix leak of inode reference on delegation failure

["J. Bruce Fields" <bfields@redhat.com>]

Acked-by: J. Bruce Fields <bfields@redhat.com>

On Tue, Nov 25, 2014 at 11:05:21AM +0200, =?UTF-8?q?Tuomas=20R=C3=A4s=C3=A4nen?= wrote:
> From: J. Bruce Fields <bfields@redhat.com>
> 
> commit bf7bd3e98be5c74813bee6ad496139fb0a011b3b upstream.
> 
> This fixes a regression from 68a3396178e6688ad7367202cdf0af8ed03c8727
> "nfsd4: shut down more of delegation earlier".
> 
> After that commit, nfs4_set_delegation() failures result in
> nfs4_put_delegation being called, but nfs4_put_delegation doesn't free
> the nfs4_file that has already been set by alloc_init_deleg().
> 
> This can result in an oops on later unmounting the exported filesystem.
> 
> Note also delaying the fi_had_conflict check we're able to return a
> better error (hence give 4.1 clients a better idea why the delegation
> failed; though note CONFLICT isn't an exact match here, as that's
> supposed to indicate a current conflict, but all we know here is that
> there was one recently).
> 
> Reported-by: Toralf Förster <toralf.foerster@gmx.de>
> Tested-by: Toralf Förster <toralf.foerster@gmx.de>
> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> [tuomasjjrasanen: backported to 3.10
>    Conflicts fs/nfsd/nfs4state.c:
>      Delegation type flags have been removed from upstream code. In 3.10-series,
>      they still exists and therefore the commit caused few conflicts in function
>      signatures.
> ]
> Signed-off-by: Tuomas Räsänen <tuomasjjrasanen@opinsys.fi>
> ---
>  fs/nfsd/nfs4state.c | 31 ++++++++++++++++++++-----------
>  1 file changed, 20 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index bdff771..836307a 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -367,7 +367,6 @@ static struct nfs4_delegation *
>  alloc_init_deleg(struct nfs4_client *clp, struct nfs4_ol_stateid *stp, struct svc_fh *current_fh, u32 type)
>  {
>  	struct nfs4_delegation *dp;
> -	struct nfs4_file *fp = stp->st_file;
>  
>  	dprintk("NFSD alloc_init_deleg\n");
>  	/*
> @@ -377,8 +376,6 @@ alloc_init_deleg(struct nfs4_client *clp, struct nfs4_ol_stateid *stp, struct sv
>  	 */
>  	if (type != NFS4_OPEN_DELEGATE_READ)
>  		return NULL;
> -	if (fp->fi_had_conflict)
> -		return NULL;
>  	if (num_delegations > max_delegations)
>  		return NULL;
>  	dp = delegstateid(nfs4_alloc_stid(clp, deleg_slab));
> @@ -395,8 +392,7 @@ alloc_init_deleg(struct nfs4_client *clp, struct nfs4_ol_stateid *stp, struct sv
>  	INIT_LIST_HEAD(&dp->dl_perfile);
>  	INIT_LIST_HEAD(&dp->dl_perclnt);
>  	INIT_LIST_HEAD(&dp->dl_recall_lru);
> -	get_nfs4_file(fp);
> -	dp->dl_file = fp;
> +	dp->dl_file = NULL;
>  	dp->dl_type = type;
>  	fh_copy_shallow(&dp->dl_fh, &current_fh->fh_handle);
>  	dp->dl_time = 0;
> @@ -2965,22 +2961,35 @@ static int nfs4_setlease(struct nfs4_delegation *dp, int flag)
>  	return 0;
>  }
>  
> -static int nfs4_set_delegation(struct nfs4_delegation *dp, int flag)
> +static int nfs4_set_delegation(struct nfs4_delegation *dp, int flag, struct nfs4_file *fp)
>  {
> -	struct nfs4_file *fp = dp->dl_file;
> +	int status;
>  
> -	if (!fp->fi_lease)
> -		return nfs4_setlease(dp, flag);
> +	if (fp->fi_had_conflict)
> +		return -EAGAIN;
> +	get_nfs4_file(fp);
> +	dp->dl_file = fp;
> +	if (!fp->fi_lease) {
> +		status = nfs4_setlease(dp, flag);
> +		if (status)
> +			goto out_free;
> +		return 0;
> +	}
>  	spin_lock(&recall_lock);
>  	if (fp->fi_had_conflict) {
>  		spin_unlock(&recall_lock);
> -		return -EAGAIN;
> +		status = -EAGAIN;
> +		goto out_free;
>  	}
>  	atomic_inc(&fp->fi_delegees);
>  	list_add(&dp->dl_perfile, &fp->fi_delegations);
>  	spin_unlock(&recall_lock);
>  	list_add(&dp->dl_perclnt, &dp->dl_stid.sc_client->cl_delegations);
>  	return 0;
> +out_free:
> +	put_nfs4_file(fp);
> +	dp->dl_file = fp;
> +	return status;
>  }
>  
>  static void nfsd4_open_deleg_none_ext(struct nfsd4_open *open, int status)
> @@ -3046,7 +3055,7 @@ nfs4_open_delegation(struct net *net, struct svc_fh *fh,
>  	dp = alloc_init_deleg(oo->oo_owner.so_client, stp, fh, flag);
>  	if (dp == NULL)
>  		goto out_no_deleg;
> -	status = nfs4_set_delegation(dp, flag);
> +	status = nfs4_set_delegation(dp, flag, stp->st_file);
>  	if (status)
>  		goto out_free;
>  
> -- 
> 2.1.3
>