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pg_resetwal: Prevent division-by-zero errors

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Handle the case where the pg_control file specifies a WAL segment size
of 0 bytes.  This would previously have led to a division by zero error.
Change this to assume the whole file is corrupt and go to guess
everything.

Discussion: https://www.postgresql.org/message-id/a6163ad7-cc99-fdd1-dfad-25df73032ab8%402ndquadrant.com
This commit is contained in:
Peter Eisentraut 2018-03-23 10:10:49 -04:00
parent 86f575948c
commit f1a074b146
2 changed files with 49 additions and 2 deletions
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4
src/bin/pg_resetwal/pg_resetwal.c
View File

@ -601,7 +601,7 @@ ReadControlFile(void)
fprintf(stderr,
_("%s: pg_control specifies invalid WAL segment size (%d bytes); proceed with caution \n"),
progname, WalSegSz);
guessed = true;
return false;
}
return true;
@ -678,7 +678,7 @@ GuessControlValues(void)
ControlFile.floatFormat = FLOATFORMAT_VALUE;
ControlFile.blcksz = BLCKSZ;
ControlFile.relseg_size = RELSEG_SIZE;
ControlFile.xlog_blcksz = XLOG_BLCKSZ;
WalSegSz = ControlFile.xlog_blcksz = XLOG_BLCKSZ;
ControlFile.xlog_seg_size = DEFAULT_XLOG_SEG_SIZE;
ControlFile.nameDataLen = NAMEDATALEN;
ControlFile.indexMaxKeys = INDEX_MAX_KEYS;

47
src/bin/pg_resetwal/t/002_corrupted.pl Normal file
View File

@ -0,0 +1,47 @@
# Tests for handling a corrupted pg_control
use strict;
use warnings;
use PostgresNode;
use TestLib;
use Test::More tests => 6;
my $node = get_new_node('main');
$node->init;
my $pg_control = $node->data_dir . '/global/pg_control';
my $size = (stat($pg_control))[7];
# Read out the head of the file to get PG_CONTROL_VERSION in
# particular.
my $data;
open my $fh, '<', $pg_control or BAIL_OUT($!);
binmode $fh;
read $fh, $data, 16;
close $fh;
# Fill pg_control with zeros
open $fh, '>', $pg_control or BAIL_OUT($!);
binmode $fh;
print $fh pack("x[$size]");
close $fh;
command_checks_all([ 'pg_resetwal', '-n', $node->data_dir ],
0,
[ qr/pg_control version number/ ],
[ qr/pg_resetwal: pg_control exists but is broken or wrong version; ignoring it/ ],
'processes corrupted pg_control all zeroes');
# Put in the previously saved header data. This uses a different code
# path internally, allowing us to process a zero WAL segment size.
open $fh, '>', $pg_control or BAIL_OUT($!);
binmode $fh;
print $fh $data, pack("x[" . ($size - 16) . "]");
close $fh;
command_checks_all([ 'pg_resetwal', '-n', $node->data_dir ],
0,
[ qr/pg_control version number/ ],
[ qr/\Qpg_resetwal: pg_control specifies invalid WAL segment size (0 bytes); proceed with caution\E/ ],
'processes zero WAL segment size');