[PATCH] nfsd4: check lock type against openmode.

We shouldn't be allowing, e.g., write locks on files not open for read. To
enforce this, we add a pointer from the lock stateid back to the open stateid
it came from, so that the check will continue to be correct even after the
open is upgraded or downgraded.

Signed-off-by: Andy Adamson <[e-mail]>
Signed-off-by: J. Bruce Fields <[e-mail]>
Signed-off-by: Neil Brown <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/nfsd/nfs4state.c

···
 	stp->st_deny_bmap = 0;
 	__set_bit(open->op_share_access, &stp->st_access_bmap);
 	__set_bit(open->op_share_deny, &stp->st_deny_bmap);
+	stp->st_openstp = NULL;
 }
 
 static void
···
 	return status;
 }
 
+static inline int
+setlkflg (int type)
+{
+	return (type == NFS4_READW_LT || type == NFS4_READ_LT) ?
+		RD_STATE : WR_STATE;
+}
 
 /* 
  * Checks for sequence id mutating operations. 
  */
 static int
-nfs4_preprocess_seqid_op(struct svc_fh *current_fh, u32 seqid, stateid_t *stateid, int flags, struct nfs4_stateowner **sopp, struct nfs4_stateid **stpp, clientid_t *lockclid)
+nfs4_preprocess_seqid_op(struct svc_fh *current_fh, u32 seqid, stateid_t *stateid, int flags, struct nfs4_stateowner **sopp, struct nfs4_stateid **stpp, struct nfsd4_lock *lock)
 {
 	struct nfs4_stateid *stp;
 	struct nfs4_stateowner *sop;
···
 		goto check_replay;
 	}
 
-	/* for new lock stateowners:
-	 * check that the lock->v.new.open_stateid
-	 * refers to an open stateowner
-	 *
-	 * check that the lockclid (nfs4_lock->v.new.clientid) is the same
-	 * as the open_stateid->st_stateowner->so_client->clientid
-	 */
-	if (lockclid) {
+	if (lock) {
 		struct nfs4_stateowner *sop = stp->st_stateowner;
+		clientid_t *lockclid = &lock->v.new.clientid;
 		struct nfs4_client *clp = sop->so_client;
+		int lkflg = 0;
+		int status;
 
-		if (!sop->so_is_open_owner)
-			return nfserr_bad_stateid;
-		if (!cmp_clid(&clp->cl_clientid, lockclid))
-			return nfserr_bad_stateid;
+		lkflg = setlkflg(lock->lk_type);
+
+		if (lock->lk_is_new) {
+                       if (!sop->so_is_open_owner)
+			       return nfserr_bad_stateid;
+                       if (!cmp_clid(&clp->cl_clientid, lockclid))
+			       return nfserr_bad_stateid;
+                       /* stp is the open stateid */
+                       status = nfs4_check_openmode(stp, lkflg);
+                       if (status)
+			       return status;
+               } else {
+                       /* stp is the lock stateid */
+                       status = nfs4_check_openmode(stp->st_openstp, lkflg);
+                       if (status)
+			       return status;
+               }
+
 	}
 
 	if ((flags & CHECK_FH) && nfs4_check_fh(current_fh, stp)) {
···
 	stp->st_vfs_file = open_stp->st_vfs_file; /* FIXME refcount?? */
 	stp->st_access_bmap = open_stp->st_access_bmap;
 	stp->st_deny_bmap = open_stp->st_deny_bmap;
+	stp->st_openstp = open_stp;
 
 out:
 	return stp;
···
 				        lock->lk_new_open_seqid,
 		                        &lock->lk_new_open_stateid,
 		                        CHECK_FH | OPEN_STATE,
-		                        &open_sop, &open_stp,
-					&lock->v.new.clientid);
+		                        &open_sop, &open_stp, lock);
 		if (status)
 			goto out;
 		/* create lockowner and lock stateid */
···
 				       lock->lk_old_lock_seqid, 
 				       &lock->lk_old_lock_stateid, 
 				       CHECK_FH | LOCK_STATE, 
-				       &lock->lk_stateowner, &lock_stp, NULL);
+				       &lock->lk_stateowner, &lock_stp, lock);
 		if (status)
 			goto out;
 	}

include/linux/nfsd/state.h

···
 *       st_perlockowner: (open stateid) list of lock nfs4_stateowners
 * 	st_access_bmap: used only for open stateid
 * 	st_deny_bmap: used only for open stateid
+*	st_openstp: open stateid lock stateid was derived from
+*
+* XXX: open stateids and lock stateids have diverged sufficiently that
+* we should consider defining separate structs for the two cases.
 */
 
 struct nfs4_stateid {
···
 	struct file                 * st_vfs_file;
 	unsigned long                 st_access_bmap;
 	unsigned long                 st_deny_bmap;
+	struct nfs4_stateid         * st_openstp;
 };
 
 /* flags for preprocess_seqid_op() */