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pg_controldata: Prevent division-by-zero errors 

If the control file is corrupted and specifies the WAL segment size
to be 0 bytes, calculating the latest checkpoint's REDO WAL file
will fail with a division-by-zero error.  Show it as "???" instead.

Also reword the warning message a bit and send it to stdout, like the
other pre-existing warning messages.

Add some tests for dealing with a corrupted pg_control file.

Author: Nathan Bossart <bossartn@amazon.com>, tests by me
This commit is contained in:
Peter Eisentraut 2018-03-21 12:14:53 -04:00
parent 56163004b8
commit 4731d848f2
2 changed files with 38 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
src/bin/pg_controldata/pg_controldata.c
View File

@ -95,7 +95,6 @@ main(int argc, char *argv[])
char mock_auth_nonce_str[MOCK_AUTH_NONCE_LEN * 2 + 1];
const char *strftime_fmt = "%c";
const char *progname;
XLogSegNo segno;
char xlogfilename[MAXFNAMELEN];
int c;
int i;
@ -169,10 +168,11 @@ main(int argc, char *argv[])
WalSegSz = ControlFile->xlog_seg_size;
if (!IsValidWalSegSize(WalSegSz))
fprintf(stderr,
_("WARNING: WAL segment size specified, %d bytes, is not a power of two between 1MB and 1GB.\n"
"The file is corrupt and the results below are untrustworthy.\n"),
WalSegSz);
printf(_("WARNING: invalid WAL segment size\n"
"The WAL segment size stored in the file, %d bytes, is not a power of two\n"
"between 1 MB and 1 GB. The file is corrupt and the results below are\n"
"untrustworthy.\n\n"),
WalSegSz);
/*
* This slightly-chintzy coding will work as long as the control file
@ -193,10 +193,20 @@ main(int argc, char *argv[])
/*
* Calculate name of the WAL file containing the latest checkpoint's REDO
* start point.
*
* A corrupted control file could report a WAL segment size of 0, and to
* guard against division by zero, we need to treat that specially.
*/
XLByteToSeg(ControlFile->checkPointCopy.redo, segno, WalSegSz);
XLogFileName(xlogfilename, ControlFile->checkPointCopy.ThisTimeLineID,
segno, WalSegSz);
if (WalSegSz != 0)
{
XLogSegNo segno;
XLByteToSeg(ControlFile->checkPointCopy.redo, segno, WalSegSz);
XLogFileName(xlogfilename, ControlFile->checkPointCopy.ThisTimeLineID,
segno, WalSegSz);
}
else
strcpy(xlogfilename, _("???"));
/*
* Format system_identifier and mock_authentication_nonce separately to

21
src/bin/pg_controldata/t/001_pg_controldata.pl
View File

@ -2,7 +2,7 @@ use strict;
use warnings;
use PostgresNode;
use TestLib;
use Test::More tests => 13;
use Test::More tests => 17;
program_help_ok('pg_controldata');
program_version_ok('pg_controldata');
@ -16,3 +16,22 @@ $node->init;
command_like([ 'pg_controldata', $node->data_dir ],
qr/checkpoint/, 'pg_controldata produces output');
# check with a corrupted pg_control
my $pg_control = $node->data_dir . '/global/pg_control';
my $size = (stat($pg_control))[7];
open my $fh, '>', $pg_control or BAIL_OUT($!);
binmode $fh;
# fill file with zeros
print $fh pack("x[$size]");
close $fh;
command_checks_all([ 'pg_controldata', $node->data_dir ],
0,
[ qr/WARNING: Calculated CRC checksum does not match value stored in file/,
qr/WARNING: invalid WAL segment size/ ],
[ qr/^$/ ],
'pg_controldata with corrupted pg_control');