[David Steele <david@pgbackrest.org>]

Hackers,

Currently check_recovery_target_timeline() converts any value that is 
not current, latest, or a valid integer to 0. So for example:

recovery_target_timeline = 'currrent'

results in the following error:

FATAL:  22023: recovery target timeline 0 does not exist

Since there is no range checking for uint32 (but there is a cast from 
unsigned long) this setting:

recovery_target_timeline = '9999999999'

results in the following error (on 64-bit):

FATAL:  22023: recovery target timeline 1410065407 does not exist

Improve by adding endptr checking to catch conversion errors and add 
range checking to exclude values < 2 and greater than UINT_MAX.

I discovered this while testing on Postgres versions < 12 where

recovery_target_timeline = 'current'

sets the target timeline to 'latest', which is a pretty surprising 
result. I'm only noting it in case somebody is searching the archives 
since the versions in question are EOL. But that odd result made me 
wonder if Postgres >= 12 had a similar problem. While it is not quite so 
confusing as Postgres < 12 I think it still bears improving.

The tests are probably excessive but I needed something to show that the 
verification works as expected.

Regards,
-David

Attachments:

timeline-log-v1.patch (text/plain, 1.6K) download
From f14e30b18cde216131bd3e069ee8ecd5da3301b0 Mon Sep 17 00:00:00 2001
From: David Steele <david@pgmasters.net>
Date: Fri, 20 Dec 2024 15:13:59 +0000
Subject: Fix logging for invalid recovery timeline.

If the requested recovery timeline is not reachable the logged checkpoint and
TLI should to be the values read from backup_label when backup_label is
present.
---
 src/backend/access/transam/xlogrecovery.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/backend/access/transam/xlogrecovery.c b/src/backend/access/transam/xlogrecovery.c
index c6994b78282..99afd01bf38 100644
--- a/src/backend/access/transam/xlogrecovery.c
+++ b/src/backend/access/transam/xlogrecovery.c
@@ -844,13 +844,13 @@ InitWalRecovery(ControlFileData *ControlFile, bool *wasShutdown_ptr,
 		 * tliSwitchPoint will throw an error if the checkpoint's timeline is
 		 * not in expectedTLEs at all.
 		 */
-		switchpoint = tliSwitchPoint(ControlFile->checkPointCopy.ThisTimeLineID, expectedTLEs, NULL);
+		switchpoint = tliSwitchPoint(CheckPointTLI, expectedTLEs, NULL);
 		ereport(FATAL,
 				(errmsg("requested timeline %u is not a child of this server's history",
 						recoveryTargetTLI),
 				 errdetail("Latest checkpoint is at %X/%X on timeline %u, but in the history of the requested timeline, the server forked off from that timeline at %X/%X.",
-						   LSN_FORMAT_ARGS(ControlFile->checkPoint),
-						   ControlFile->checkPointCopy.ThisTimeLineID,
+						   LSN_FORMAT_ARGS(CheckPointLoc),
+						   CheckPointTLI,
 						   LSN_FORMAT_ARGS(switchpoint))));
 	}
 
-- 
2.34.1