From be40dd63e00d4ccb1bc10cab5c086a6e544c3a30 Mon Sep 17 00:00:00 2001 From: Nathan Bossart Date: Thu, 27 Apr 2023 13:43:48 -0700 Subject: [PATCH] Prevent underflow in KeepLogSeg(). The call to XLogGetReplicationSlotMinimumLSN() might return a greater LSN than the one given to the function. Subsequent segment number calculations might then underflow, which could result in unexpected behavior when removing or recyling WAL files. This was introduced with max_slot_wal_keep_size in c655077639. To fix, skip the block of code for replication slots if the LSN is greater. Reported-by: Xu Xingwang Author: Kyotaro Horiguchi Reviewed-by: Junwang Zhao Discussion: https://postgr.es/m/17903-4288d439dee856c6%40postgresql.org Backpatch-through: 13 --- src/backend/access/transam/xlog.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index d53a8afd38..a1ceded9e0 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -9836,7 +9836,7 @@ KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo) * max_slot_wal_keep_size. */ keep = XLogGetReplicationSlotMinimumLSN(); - if (keep != InvalidXLogRecPtr) + if (keep != InvalidXLogRecPtr && keep < recptr) { XLByteToSeg(keep, segno, wal_segment_size);