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Commit4731d84

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pg_controldata: Prevent division-by-zero errors
If the control file is corrupted and specifies the WAL segment sizeto be 0 bytes, calculating the latest checkpoint's REDO WAL filewill fail with a division-by-zero error. Show it as "???" instead.Also reword the warning message a bit and send it to stdout, like theother pre-existing warning messages.Add some tests for dealing with a corrupted pg_control file.Author: Nathan Bossart <bossartn@amazon.com>, tests by me
1 parent5616300 commit4731d84

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2 files changed

+38
-9
lines changed

2 files changed

+38
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lines changed

‎src/bin/pg_controldata/pg_controldata.c

Lines changed: 18 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -95,7 +95,6 @@ main(int argc, char *argv[])
9595
charmock_auth_nonce_str[MOCK_AUTH_NONCE_LEN*2+1];
9696
constchar*strftime_fmt="%c";
9797
constchar*progname;
98-
XLogSegNosegno;
9998
charxlogfilename[MAXFNAMELEN];
10099
intc;
101100
inti;
@@ -169,10 +168,11 @@ main(int argc, char *argv[])
169168
WalSegSz=ControlFile->xlog_seg_size;
170169

171170
if (!IsValidWalSegSize(WalSegSz))
172-
fprintf(stderr,
173-
_("WARNING: WAL segment size specified, %d bytes, is not a power of two between 1MB and 1GB.\n"
174-
"The file is corrupt and the results below are untrustworthy.\n"),
175-
WalSegSz);
171+
printf(_("WARNING: invalid WAL segment size\n"
172+
"The WAL segment size stored in the file, %d bytes, is not a power of two\n"
173+
"between 1 MB and 1 GB. The file is corrupt and the results below are\n"
174+
"untrustworthy.\n\n"),
175+
WalSegSz);
176176

177177
/*
178178
* This slightly-chintzy coding will work as long as the control file
@@ -193,10 +193,20 @@ main(int argc, char *argv[])
193193
/*
194194
* Calculate name of the WAL file containing the latest checkpoint's REDO
195195
* start point.
196+
*
197+
* A corrupted control file could report a WAL segment size of 0, and to
198+
* guard against division by zero, we need to treat that specially.
196199
*/
197-
XLByteToSeg(ControlFile->checkPointCopy.redo,segno,WalSegSz);
198-
XLogFileName(xlogfilename,ControlFile->checkPointCopy.ThisTimeLineID,
199-
segno,WalSegSz);
200+
if (WalSegSz!=0)
201+
{
202+
XLogSegNosegno;
203+
204+
XLByteToSeg(ControlFile->checkPointCopy.redo,segno,WalSegSz);
205+
XLogFileName(xlogfilename,ControlFile->checkPointCopy.ThisTimeLineID,
206+
segno,WalSegSz);
207+
}
208+
else
209+
strcpy(xlogfilename,_("???"));
200210

201211
/*
202212
* Format system_identifier and mock_authentication_nonce separately to

‎src/bin/pg_controldata/t/001_pg_controldata.pl

Lines changed: 20 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@
22
use warnings;
33
use PostgresNode;
44
use TestLib;
5-
use Test::Moretests=>13;
5+
use Test::Moretests=>17;
66

77
program_help_ok('pg_controldata');
88
program_version_ok('pg_controldata');
@@ -16,3 +16,22 @@
1616

1717
command_like(['pg_controldata',$node->data_dir ],
1818
qr/checkpoint/,'pg_controldata produces output');
19+
20+
21+
# check with a corrupted pg_control
22+
23+
my$pg_control =$node->data_dir .'/global/pg_control';
24+
my$size = (stat($pg_control))[7];
25+
26+
openmy$fh,'>',$pg_controlor BAIL_OUT($!);
27+
binmode$fh;
28+
# fill file with zeros
29+
print$fhpack("x[$size]");
30+
close$fh;
31+
32+
command_checks_all(['pg_controldata',$node->data_dir ],
33+
0,
34+
[qr/WARNING: Calculated CRC checksum does not match value stored in file/,
35+
qr/WARNING: invalid WAL segment size/ ],
36+
[qr/^$/ ],
37+
'pg_controldata with corrupted pg_control');

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