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Commit78e4fb8

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committed
Prevent running pg_resetwal/pg_resetxlog against wrong-version data dirs.
pg_resetwal (formerly pg_resetxlog) doesn't insist on finding a matchingversion number in pg_control, and that seems like an important thing topreserve since recovering from corrupt pg_control is a prime reason toneed to run it. However, that means you can try to run it against adata directory of a different major version, which is at best uselessand at worst disastrous. So as to provide some protection against thattype of pilot error, inspect PG_VERSION at startup and refuse to doanything if it doesn't match. PG_VERSION is read-only after initdb,so it's unlikely to get corrupted, and even if it were corrupted it wouldbe easy to fix by hand.This hazard has been there all along, so back-patch to all supportedbranches.Michael Paquier, with some kibitzing by meDiscussion:https://postgr.es/m/f4b8eb91-b934-8a0d-b3cc-68f06e2279d1@enterprisedb.com
1 parent7d9309f commit78e4fb8

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2 files changed

+74
-1
lines changed

2 files changed

+74
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lines changed

‎doc/src/sgml/ref/pg_resetxlog.sgml

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -203,6 +203,11 @@ PostgreSQL documentation
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<command>pg_resetxlog</command> to run. But before you do
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so, make doubly certain that there is no server process still alive.
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</para>
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<para>
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<command>pg_resetxlog</command> works only with servers of the same
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major version.
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</para>
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</refsect1>
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</refentry>

‎src/bin/pg_resetxlog/pg_resetxlog.c

Lines changed: 69 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -69,6 +69,7 @@ static const char *progname;
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staticchar*restrict_env;
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#endif
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72+
staticvoidCheckDataVersion(void);
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staticboolReadControlFile(void);
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staticvoidGuessControlValues(void);
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staticvoidPrintControlValues(boolguessed);
@@ -278,6 +279,9 @@ main(int argc, char *argv[])
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exit(1);
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}
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/* Check that data directory matches our server version */
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CheckDataVersion();
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281285
/*
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* Check for a postmaster lock file --- if there is one, refuse to
283287
* proceed, on grounds we might be interfering with a live installation.
@@ -399,6 +403,70 @@ main(int argc, char *argv[])
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}
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/*
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* Look at the version string stored in PG_VERSION and decide if this utility
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* can be run safely or not.
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*
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* We don't want to inject pg_control and WAL files that are for a different
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* major version; that can't do anything good. Note that we don't treat
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* mismatching version info in pg_control as a reason to bail out, because
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* recovering from a corrupted pg_control is one of the main reasons for this
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* program to exist at all. However, PG_VERSION is unlikely to get corrupted,
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* and if it were it would be easy to fix by hand. So let's make this check
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* to prevent simple user errors.
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*/
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staticvoid
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CheckDataVersion(void)
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{
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constchar*ver_file="PG_VERSION";
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FILE*ver_fd;
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charrawline[64];
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intlen;
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if ((ver_fd=fopen(ver_file,"r"))==NULL)
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{
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fprintf(stderr,_("%s: could not open file \"%s\" for reading: %s\n"),
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progname,ver_file,strerror(errno));
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exit(1);
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}
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/* version number has to be the first line read */
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if (!fgets(rawline,sizeof(rawline),ver_fd))
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{
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if (!ferror(ver_fd))
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{
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fprintf(stderr,_("%s: unexpected empty file \"%s\"\n"),
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progname,ver_file);
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}
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else
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{
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fprintf(stderr,_("%s: could not read file \"%s\": %s\n"),
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progname,ver_file,strerror(errno));
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}
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exit(1);
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}
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/* remove trailing newline, handling Windows newlines as well */
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len=strlen(rawline);
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if (len>0&&rawline[len-1]=='\n')
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{
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rawline[--len]='\0';
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if (len>0&&rawline[len-1]=='\r')
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rawline[--len]='\0';
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}
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if (strcmp(rawline,PG_MAJORVERSION)!=0)
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{
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fprintf(stderr,_("%s: data directory is of wrong version\n"
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"File \"%s\" contains \"%s\", which is not compatible with this program's version \"%s\".\n"),
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progname,ver_file,rawline,PG_MAJORVERSION);
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exit(1);
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}
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fclose(ver_fd);
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}
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402470
/*
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* Try to read the existing pg_control file.
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*
@@ -468,7 +536,7 @@ ReadControlFile(void)
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}
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470538
/* Looks like it's a mess. */
471-
fprintf(stderr,_("%s: pg_control exists but is broken orunknown version; ignoring it\n"),
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fprintf(stderr,_("%s: pg_control exists but is broken orwrong version; ignoring it\n"),
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progname);
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return false;
474542
}

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