s3: Add a "lock_order" argument to db_open

This will be used to enforce a lock hierarchy between the databases. We have
seen deadlocks between locking.tdb, brlock.tdb, serverid.tdb and notify*.tdb.
These should be fixed by refusing a dbwrap_fetch_locked that does not follow a
defined lock hierarchy.

8 files changed, 36 insertions, 8 deletions

diff --git a/source3/lib/conn_tdb.c b/source3/lib/conn_tdb.c
index f600871411..9b0a07a56c 100644
--- a/source3/lib/conn_tdb.c
+++ b/source3/lib/conn_tdb.c
@@ -36,7 +36,8 @@ static struct db_context *connections_db_ctx(bool rw)
 	open_flags = rw ? (O_RDWR|O_CREAT) : O_RDONLY;
 
 	db_ctx = db_open(NULL, lock_path("connections.tdb"), 0,
-			 TDB_CLEAR_IF_FIRST|TDB_INCOMPATIBLE_HASH|TDB_DEFAULT, open_flags, 0644);
+			 TDB_CLEAR_IF_FIRST|TDB_INCOMPATIBLE_HASH|TDB_DEFAULT,
+			 open_flags, 0644, DBWRAP_LOCK_ORDER_1);
 	return db_ctx;
 }
 
diff --git a/source3/lib/dbwrap/dbwrap_open.c b/source3/lib/dbwrap/dbwrap_open.c
index 6b8be2de16..23d299511b 100644
--- a/source3/lib/dbwrap/dbwrap_open.c
+++ b/source3/lib/dbwrap/dbwrap_open.c
@@ -62,11 +62,26 @@ bool db_is_local(const char *name)
 struct db_context *db_open(TALLOC_CTX *mem_ctx,
 			   const char *name,
 			   int hash_size, int tdb_flags,
-			   int open_flags, mode_t mode)
+			   int open_flags, mode_t mode,
+			   enum dbwrap_lock_order lock_order)
 {
 	struct db_context *result = NULL;
 #ifdef CLUSTER_SUPPORT
-	const char *sockname = lp_ctdbd_socket();
+	const char *sockname;
+#endif
+
+	if ((lock_order != DBWRAP_LOCK_ORDER_1) &&
+	    (lock_order != DBWRAP_LOCK_ORDER_2)) {
+		/*
+		 * Only allow 2 levels. ctdb gives us 3, and we will
+		 * have the watchers database soon.
+		 */
+		errno = EINVAL;
+		return NULL;
+	}
+
+#ifdef CLUSTER_SUPPORT
+	sockname = lp_ctdbd_socket();
 
 	if(!sockname || !*sockname) {
 		sockname = CTDB_PATH;
diff --git a/source3/lib/dbwrap/dbwrap_open.h b/source3/lib/dbwrap/dbwrap_open.h
index 5a172a4a2a..2763ef2ade 100644
--- a/source3/lib/dbwrap/dbwrap_open.h
+++ b/source3/lib/dbwrap/dbwrap_open.h
@@ -29,6 +29,11 @@ struct db_context;
  */
 bool db_is_local(const char *name);
 
+enum dbwrap_lock_order {
+	DBWRAP_LOCK_ORDER_1 = 1,
+	DBWRAP_LOCK_ORDER_2 = 2
+};
+
 /**
  * Convenience function that will determine whether to
  * open a tdb database via the tdb backend or via the ctdb
@@ -38,6 +43,7 @@ bool db_is_local(const char *name);
 struct db_context *db_open(TALLOC_CTX *mem_ctx,
 			   const char *name,
 			   int hash_size, int tdb_flags,
-			   int open_flags, mode_t mode);
+			   int open_flags, mode_t mode,
+			   enum dbwrap_lock_order lock_order);
 
 #endif /* __DBWRAP_OPEN_H__ */
diff --git a/source3/lib/dbwrap/dbwrap_private.h b/source3/lib/dbwrap/dbwrap_private.h
index 4806618543..d0b3279368 100644
--- a/source3/lib/dbwrap/dbwrap_private.h
+++ b/source3/lib/dbwrap/dbwrap_private.h
@@ -23,6 +23,8 @@
 #ifndef __DBWRAP_PRIVATE_H__
 #define __DBWRAP_PRIVATE_H__
 
+#include "dbwrap/dbwrap_open.h"
+
 struct db_record {
 	TDB_DATA key, value;
 	NTSTATUS (*store)(struct db_record *rec, TDB_DATA data, int flag);
diff --git a/source3/lib/g_lock.c b/source3/lib/g_lock.c
index 561617023f..1fd8ae9f38 100644
--- a/source3/lib/g_lock.c
+++ b/source3/lib/g_lock.c
@@ -60,7 +60,8 @@ struct g_lock_ctx *g_lock_ctx_init(TALLOC_CTX *mem_ctx,
 
 	result->db = db_open(result, lock_path("g_lock.tdb"), 0,
 			     TDB_CLEAR_IF_FIRST|TDB_INCOMPATIBLE_HASH,
-			     O_RDWR|O_CREAT, 0600);
+			     O_RDWR|O_CREAT, 0600,
+			     DBWRAP_LOCK_ORDER_2);
 	if (result->db == NULL) {
 		DEBUG(1, ("g_lock_init: Could not open g_lock.tdb\n"));
 		TALLOC_FREE(result);
diff --git a/source3/lib/serverid.c b/source3/lib/serverid.c
index 6d8a3c004f..6a8083a7a2 100644
--- a/source3/lib/serverid.c
+++ b/source3/lib/serverid.c
@@ -76,7 +76,8 @@ static struct db_context *serverid_db(void)
 		return db;
 	}
 	db = db_open(NULL, lock_path("serverid.tdb"), 0,
-		     TDB_DEFAULT|TDB_CLEAR_IF_FIRST|TDB_INCOMPATIBLE_HASH, O_RDWR|O_CREAT, 0644);
+		     TDB_DEFAULT|TDB_CLEAR_IF_FIRST|TDB_INCOMPATIBLE_HASH,
+		     O_RDWR|O_CREAT, 0644, DBWRAP_LOCK_ORDER_2);
 	return db;
 }
 
diff --git a/source3/lib/sessionid_tdb.c b/source3/lib/sessionid_tdb.c
index 6fd3bbc487..5782c9a544 100644
--- a/source3/lib/sessionid_tdb.c
+++ b/source3/lib/sessionid_tdb.c
@@ -34,7 +34,8 @@ static struct db_context *session_db_ctx(void)
 
 	session_db_ctx_ptr = db_open(NULL, lock_path("sessionid.tdb"), 0,
 				     TDB_CLEAR_IF_FIRST|TDB_DEFAULT|TDB_INCOMPATIBLE_HASH,
-				     O_RDWR | O_CREAT, 0644);
+				     O_RDWR | O_CREAT, 0644,
+				     DBWRAP_LOCK_ORDER_1);
 	return session_db_ctx_ptr;
 }
 
diff --git a/source3/lib/sharesec.c b/source3/lib/sharesec.c
index 2c324cf971..cb8993cc8e 100644
--- a/source3/lib/sharesec.c
+++ b/source3/lib/sharesec.c
@@ -148,7 +148,8 @@ bool share_info_db_init(void)
 	}
 
 	share_db = db_open(NULL, state_path("share_info.tdb"), 0,
-				 TDB_DEFAULT, O_RDWR|O_CREAT, 0600);
+			   TDB_DEFAULT, O_RDWR|O_CREAT, 0600,
+			   DBWRAP_LOCK_ORDER_1);
 	if (share_db == NULL) {
 		DEBUG(0,("Failed to open share info database %s (%s)\n",
 			state_path("share_info.tdb"), strerror(errno) ));