Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commitf369815

Browse files
committed
Add missing buffer lock acquisition in GetTupleForTrigger().
If we had not been holding buffer pin continuously since the tuple wasinitially fetched by the UPDATE or DELETE query, it would be possible forVACUUM or a page-prune operation to move the tuple while we're trying tocopy it. This would result in a garbage "old" tuple value being passed toan AFTER ROW UPDATE or AFTER ROW DELETE trigger. The preconditions forthis are somewhat improbable, and the timing constraints are very tight;so it's not so surprising that this hasn't been reported from the field,even though the bug has been there a long time.Problem found by Andres Freund. Back-patch to all active branches.
1 parent31c341a commitf369815

File tree

1 file changed

+12
-0
lines changed

1 file changed

+12
-0
lines changed

‎src/backend/commands/trigger.c

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2447,6 +2447,16 @@ ltrmark:;
24472447

24482448
buffer=ReadBuffer(relation,ItemPointerGetBlockNumber(tid));
24492449

2450+
/*
2451+
* Although we already know this tuple is valid, we must lock the
2452+
* buffer to ensure that no one has a buffer cleanup lock; otherwise
2453+
* they might move the tuple while we try to copy it. But we can
2454+
* release the lock before actually doing the heap_copytuple call,
2455+
* since holding pin is sufficient to prevent anyone from getting a
2456+
* cleanup lock they don't already hold.
2457+
*/
2458+
LockBuffer(buffer,BUFFER_LOCK_SHARE);
2459+
24502460
page=BufferGetPage(buffer);
24512461
lp=PageGetItemId(page,ItemPointerGetOffsetNumber(tid));
24522462

@@ -2456,6 +2466,8 @@ ltrmark:;
24562466
tuple.t_len=ItemIdGetLength(lp);
24572467
tuple.t_self=*tid;
24582468
tuple.t_tableOid=RelationGetRelid(relation);
2469+
2470+
LockBuffer(buffer,BUFFER_LOCK_UNLOCK);
24592471
}
24602472

24612473
result=heap_copytuple(&tuple);

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp