Fix assertion failure and segmentation fault in backup code.

MasaoFujii · MasaoFujii · commit b24b2be119c4 · 2022-07-20T09:57:01.000+09:00
When a non-exclusive backup is canceled, do_pg_abort_backup() is called and resets some variables set by pg_backup_start (pg_start_backup in v14 or before). But previously it forgot to reset the session state indicating whether a non-exclusive backup is in progress or not in this session. This issue could cause an assertion failure when the session running BASE_BACKUP is terminated after it executed pg_backup_start and pg_backup_stop (pg_stop_backup in v14 or before). Also it could cause a segmentation fault when pg_backup_stop is called after BASE_BACKUP in the same session is canceled. This commit fixes the issue by making do_pg_abort_backup reset that session state. Back-patch to all supported branches. Author: Fujii Masao Reviewed-by: Kyotaro Horiguchi, Masahiko Sawada, Michael Paquier, Robert Haas Discussion: https://postgr.es/m/3374718f-9fbf-a950-6d66-d973e027f44c@oss.nttdata.com
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
@@ -8791,6 +8791,8 @@ do_pg_abort_backup(int code, Datum arg)
 	{
 		XLogCtl->Insert.forcePageWrites = false;
 	}
+
+	sessionBackupState = SESSION_BACKUP_NONE;
 	WALInsertLockRelease();
 
 	if (emit_warning)

Original file line number	Diff line number	Diff line change
`@@ -8791,6 +8791,8 @@ do_pg_abort_backup(int code, Datum arg)`
`8791`	`8791`	`{`
`8792`	`8792`	`XLogCtl->Insert.forcePageWrites = false;`
`8793`	`8793`	`}`
	`8794`	`+`
	`8795`	`+ sessionBackupState = SESSION_BACKUP_NONE;`
`8794`	`8796`	`WALInsertLockRelease();`
`8795`	`8797`
`8796`	`8798`	`if (emit_warning)`