From: Robert Haas <rhaas@postgresql.org>
Date: Fri, 6 Sep 2019 12:22:32 +0000 (-0400)
Subject: When performing a base backup, check for read errors.
X-Git-Tag: REL9_5_20~72
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f697c6396d73c1e6d550afed84a6bd8362d9a0d4;p=thirdparty%2Fpostgresql.git

When performing a base backup, check for read errors.

The old code didn't differentiate between a read error and a
concurrent truncation. fread reports both of these by returning 0;
you have to use feof() or ferror() to distinguish between them,
which this code did not do.

It might be a better idea to use read() rather than fread() here,
so that we can display a less-generic error message, but I'm not
sure that would qualify as a back-patchable bug fix, so just do
this much for now.

Jeevan Chalke, reviewed by Jeevan Ladhe and by me.

Discussion: http://postgr.es/m/CA+TgmobG4ywMzL5oQq2a8YKp8x2p3p1LOMMcGqpS7aekT9+ETA@mail.gmail.com
---

diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 8259ec5bd89..ddb1de0621d 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -84,6 +84,18 @@ static char *statrelpath = NULL;
  */
 #define THROTTLING_FREQUENCY	8
 
+/*
+ * Checks whether we encountered any error in fread().  fread() doesn't give
+ * any clue what has happened, so we check with ferror().  Also, neither
+ * fread() nor ferror() set errno, so we just throw a generic error.
+ */
+#define CHECK_FREAD_ERROR(fp, filename) \
+do { \
+	if (ferror(fp)) \
+		ereport(ERROR, \
+				(errmsg("could not read from file \"%s\"", filename))); \
+} while (0)
+
 /* The actual number of bytes, transfer of which may cause sleep. */
 static uint64 throttling_sample;
 
@@ -434,6 +446,8 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 					break;
 			}
 
+			CHECK_FREAD_ERROR(fp, pathbuf);
+
 			if (len != XLogSegSize)
 			{
 				CheckXLogRemoved(segno, tli);
@@ -1173,6 +1187,8 @@ sendFile(char *readfilename, char *tarfilename, struct stat * statbuf,
 		}
 	}
 
+	CHECK_FREAD_ERROR(fp, readfilename);
+
 	/* If the file was truncated while we were sending it, pad it with zeros */
 	if (len < statbuf->st_size)
 	{