Fix race in astdb

The underlying db1 implementation does not fully isolate the pages retrieved
from astdb, so the lock protecting accesses needs to be extended until the
copy from the shared memory structure is done.
(closes issue #14682)
 Reported by: makoto


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@182449 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/db.c

@@ -187,10 +187,8 @@ int ast_db_get(const char *family, const char *keys, char *value, int valuelen)
 	memset(value, 0, valuelen);
 	key.data = fullkey;
 	key.size = fullkeylen + 1;
-	
+
 	res = astdb->get(astdb, &key, &data, 0);
-	
-	ast_mutex_unlock(&dblock);
 
 	/* Be sure to NULL terminate our data either way */
 	if (res) {
@@ -208,6 +206,11 @@ int ast_db_get(const char *family, const char *keys, char *value, int valuelen)
 			ast_log(LOG_NOTICE, "Strange, empty value for /%s/%s\n", family, keys);
 		}
 	}
+
+	/* Data is not fully isolated for concurrency, so the lock must be extended
+	 * to after the copy to the output buffer. */
+	ast_mutex_unlock(&dblock);
+
 	return res;
 }