tdb: fix an early release of the global lock that can cause data corruption

[samba.git] / lib / tdb / common / transaction.c

diff --git a/lib/tdb/common/transaction.c b/lib/tdb/common/transaction.c
index 20f2bfc2cd4595a27114fc9662c483c83b72b29d..b8988ea8301d807600f14925e756a9356848ea23 100644 (file)
--- a/lib/tdb/common/transaction.c
+++ b/lib/tdb/common/transaction.c
@@ -135,6 +135,9 @@ struct tdb_transaction {
        bool prepared;
        tdb_off_t magic_offset;
 
+       /* set when the GLOBAL_LOCK has been taken */
+       bool global_lock_taken;
+
        /* old file size before transaction */
        tdb_len_t old_map_size;
 
@@ -603,6 +606,11 @@ int _tdb_transaction_cancel(struct tdb_context *tdb)
                }
        }
 
+       if (tdb->transaction->global_lock_taken) {
+               tdb_brlock(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+               tdb->transaction->global_lock_taken = false;
+       }
+
        /* remove any global lock created during the transaction */
        if (tdb->global_lock.count != 0) {
                tdb_brlock(tdb, FREELIST_TOP, F_UNLCK, F_SETLKW, 0, 4*tdb->header.hash_size);
@@ -947,11 +955,12 @@ static int _tdb_transaction_prepare_commit(struct tdb_context *tdb)
                return -1;
        }
 
+       tdb->transaction->global_lock_taken = true;
+
        if (!(tdb->flags & TDB_NOSYNC)) {
                /* write the recovery data to the end of the file */
                if (transaction_setup_recovery(tdb, &tdb->transaction->magic_offset) == -1) {
                        TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: failed to setup recovery data\n"));
-                       tdb_brlock(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
                        _tdb_transaction_cancel(tdb);
                        return -1;
                }
@@ -966,7 +975,6 @@ static int _tdb_transaction_prepare_commit(struct tdb_context *tdb)
                                             tdb->transaction->old_map_size) == -1) {
                        tdb->ecode = TDB_ERR_IO;
                        TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: expansion failed\n"));
-                       tdb_brlock(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
                        _tdb_transaction_cancel(tdb);
                        return -1;
                }
@@ -1056,7 +1064,6 @@ int tdb_transaction_commit(struct tdb_context *tdb)
                        tdb_transaction_recover(tdb); 
 
                        _tdb_transaction_cancel(tdb);
-                       tdb_brlock(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
 
                        TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed\n"));
                        return -1;
@@ -1072,8 +1079,6 @@ int tdb_transaction_commit(struct tdb_context *tdb)
                return -1;
        }
 
-       tdb_brlock(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
-
        /*
          TODO: maybe write to some dummy hdr field, or write to magic
          offset without mmap, before the last sync, instead of the