From: Andres Freund <andres@anarazel.de>
Date: Fri, 25 Feb 2022 18:40:32 +0000 (-0800)
Subject: pg_waldump: Fix error message for WAL files smaller than XLOG_BLCKSZ.
X-Git-Tag: REL_11_16~64
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=51c34165614bde5d44a356ba5f1f4f79d8893103;p=thirdparty%2Fpostgresql.git

pg_waldump: Fix error message for WAL files smaller than XLOG_BLCKSZ.

When opening a WAL file smaller than XLOG_BLCKSZ (e.g. 0 bytes long) while
determining the wal_segment_size, pg_waldump checked errno, despite errno not
being set by the short read. Resulting in a bogus error message.

Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://postgr.es/m/20220214.181847.775024684568733277.horikyota.ntt@gmail.com
Backpatch: 11-, the bug was introducedin fc49e24fa
---

diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index 639bfcd7f7d..cd202a50ced 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -210,8 +210,10 @@ search_directory(const char *directory, const char *fname)
 	if (fd >= 0)
 	{
 		PGAlignedXLogBlock buf;
+		int			r;
 
-		if (read(fd, buf.data, XLOG_BLCKSZ) == XLOG_BLCKSZ)
+		r = read(fd, buf.data, XLOG_BLCKSZ);
+		if (r == XLOG_BLCKSZ)
 		{
 			XLogLongPageHeader longhdr = (XLogLongPageHeader) buf.data;
 
@@ -223,14 +225,12 @@ search_directory(const char *directory, const char *fname)
 									 WalSegSz),
 							fname, WalSegSz);
 		}
+		else if (r < 0)
+			fatal_error("could not read file \"%s\": %s",
+						fname, strerror(errno));
 		else
-		{
-			if (errno != 0)
-				fatal_error("could not read file \"%s\": %s",
-							fname, strerror(errno));
-			else
-				fatal_error("not enough data in file \"%s\"", fname);
-		}
+			fatal_error("not enough data in file \"%s\"", fname);
+
 		close(fd);
 		return true;
 	}