Commit fc5a96c3 authored by Jeff Layton's avatar Jeff Layton Committed by J. Bruce Fields
Browse files

nfsd: close potential race in nfsd4_free_stateid 



Once we remove the client_mutex, it'll be possible for the sc_type of a
lock stateid to change after it's found and checked, but before we can
go to destroy it. If that happens, we can end up putting the persistent
reference to the stateid more than once, and unhash it more than once.

Fix this by unhashing the lock stateid prior to dropping the cl_lock but
after finding it.

Signed-off-by: default avatarJeff Layton <jlayton@primarydata.com>
Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent 3c1c995c

fs/nfsd/nfs4state.c

+9 −12
Original line number Diff line number Diff line
@@ -4397,17 +4397,6 @@ unlock_state: 
	return status;

}



static __be32

nfsd4_free_lock_stateid(struct nfs4_ol_stateid *stp)

{

	struct nfs4_lockowner *lo = lockowner(stp->st_stateowner);



	if (check_for_locks(stp->st_stid.sc_file, lo))

		return nfserr_locks_held;

	release_lock_stateid(stp);

	return nfs_ok;

}



/*

 * Test if the stateid is valid

 */
@@ -4434,6 +4423,7 @@ nfsd4_free_stateid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, 
	stateid_t *stateid = &free_stateid->fr_stateid;

	struct nfs4_stid *s;

	struct nfs4_delegation *dp;

	struct nfs4_ol_stateid *stp;

	struct nfs4_client *cl = cstate->session->se_client;

	__be32 ret = nfserr_bad_stateid;
@@ -4456,8 +4446,15 @@ nfsd4_free_stateid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, 
		ret = check_stateid_generation(stateid, &s->sc_stateid, 1);

		if (ret)

			break;

		stp = openlockstateid(s);

		ret = nfserr_locks_held;

		if (check_for_locks(stp->st_stid.sc_file,

				    lockowner(stp->st_stateowner)))

			break;

		unhash_lock_stateid(stp);

		spin_unlock(&cl->cl_lock);

		ret = nfsd4_free_lock_stateid(openlockstateid(s));

		nfs4_put_stid(s);

		ret = nfs_ok;

		goto out;

	case NFS4_REVOKED_DELEG_STID:

		dp = delegstateid(s);

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