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* dlist_check: add check for nodes pointing to themselves
@ 2026-03-17 12:56 =?utf-8?B?5p2o56OK?= <[email protected]>
2026-04-08 15:46 ` Re: dlist_check: add check for nodes pointing to themselves [email protected] <[email protected]>
0 siblings, 1 reply; 2+ messages in thread
From: =?utf-8?B?5p2o56OK?= @ 2026-03-17 12:56 UTC (permalink / raw)
To: =?utf-8?B?cGdzcWwtaGFja2Vycw==?= <[email protected]>
Hi hackers,
I accidentally called the function dlist_push_head consecutively on the same node,
inserting it into a doubly linked list, which caused an infinite loop.
After adding the compile parameter -DILIST_DEBUG, an infinite loop occurred in the dlist_check function,
revealing that the next pointer of the current node was pointing to itself.
I am attempting to fix this issue with the following patch.
regards,
Lei Yang
Attachments:
[application/octet-stream] 0001-dlist_check-add-check-for-nodes-pointing-to-themselv.patch (1.0K, 2-0001-dlist_check-add-check-for-nodes-pointing-to-themselv.patch)
download | inline diff:
From 016a2c695a55f32a9df0e77ee9142c86c9a8f70d Mon Sep 17 00:00:00 2001
From: Lei Yang <[email protected]>
Date: Tue, 17 Mar 2026 20:51:28 +0800
Subject: [PATCH] dlist_check: add check for nodes pointing to themselves
---
src/backend/lib/ilist.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/src/backend/lib/ilist.c b/src/backend/lib/ilist.c
index d238858e24f..27dac796fd2 100644
--- a/src/backend/lib/ilist.c
+++ b/src/backend/lib/ilist.c
@@ -91,7 +91,8 @@ dlist_check(const dlist_head *head)
cur->next == NULL ||
cur->prev == NULL ||
cur->prev->next != cur ||
- cur->next->prev != cur)
+ cur->next->prev != cur ||
+ cur->next == cur)
elog(ERROR, "doubly linked list is corrupted");
}
@@ -102,7 +103,8 @@ dlist_check(const dlist_head *head)
cur->next == NULL ||
cur->prev == NULL ||
cur->prev->next != cur ||
- cur->next->prev != cur)
+ cur->next->prev != cur ||
+ cur->prev == cur)
elog(ERROR, "doubly linked list is corrupted");
}
}
--
2.34.1
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: dlist_check: add check for nodes pointing to themselves
2026-03-17 12:56 dlist_check: add check for nodes pointing to themselves =?utf-8?B?5p2o56OK?= <[email protected]>
@ 2026-04-08 15:46 ` [email protected] <[email protected]>
0 siblings, 0 replies; 2+ messages in thread
From: [email protected] @ 2026-04-08 15:46 UTC (permalink / raw)
To: yanglei <[email protected]>; +Cc: pgsql-hackers <[email protected]>
Currently, postgresql will enter an infinite loop when calling dlist_push_head the second time.
After applying this patch, it will report ERROR: doubly linked list is corrupted.
test case:
./configure --enable-debug CFLAGS='-O0 -DILIST_DEBUG' --enable-cassert
PG_FUNCTION_INFO_V1(test_dlist);
Datum
test_dlist(PG_FUNCTION_ARGS)
{
dlist_head head;
dlist_node *n;
n = palloc0(sizeof(dlist_node));
dlist_init(&head);
dlist_push_head(&head, n);
dlist_push_head(&head, n);
PG_RETURN_NULL();
}
regards,
Lei Yang
From: 杨磊
Date: 2026-03-17 20:56
To: pgsql-hackers
Subject: dlist_check: add check for nodes pointing to themselves
Hi hackers,
I accidentally called the function dlist_push_head consecutively on the same node,
inserting it into a doubly linked list, which caused an infinite loop.
After adding the compile parameter -DILIST_DEBUG, an infinite loop occurred in the dlist_check function,
revealing that the next pointer of the current node was pointing to itself.
I am attempting to fix this issue with the following patch.
regards,
Lei Yang
^ permalink raw reply [nested|flat] 2+ messages in thread
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