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Commitbecfbdd

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Fix edge-case for xl_tot_len broken bybae868c.
bae868c removed a check that was still needed. If you had anxl_tot_len at the end of a page that was too small for a record header,but not big enough to span onto the next page, we'd immediately performthe CRC check using a bogus large length. Because of arbitrary codingdifferences between the CRC implementations on different platforms,nothing very bad happened on common modern systems. On systems usingthe _sb8.c fallback we could segfault.Restore that check, add a new assertion and supply a test for that case.Back-patch to 12, likebae868c.Tested-by: Tom Lane <tgl@sss.pgh.pa.us>Tested-by: Alexander Lakhin <exclusion@gmail.com>Discussion:https://postgr.es/m/CA%2BhUKGLCkTT7zYjzOxuLGahBdQ%3DMcF%3Dz5ZvrjSOnW4EDhVjT-g%40mail.gmail.com
1 parent13aeaf0 commitbecfbdd

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2 files changed

+24
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‎src/backend/access/transam/xlogreader.c‎

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Original file line numberDiff line numberDiff line change
@@ -653,6 +653,15 @@ XLogDecodeNextRecord(XLogReaderState *state, bool nonblocking)
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}
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else
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{
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/* There may be no next page if it's too small. */
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if (total_len<SizeOfXLogRecord)
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{
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report_invalid_record(state,
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"invalid record length at %X/%X: expected at least %u, got %u",
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LSN_FORMAT_ARGS(RecPtr),
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(uint32)SizeOfXLogRecord,total_len);
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gotoerr;
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}
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/* We'll validate the header once we have the next page. */
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gotheader= false;
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}
@@ -1190,6 +1199,8 @@ ValidXLogRecord(XLogReaderState *state, XLogRecord *record, XLogRecPtr recptr)
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{
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pg_crc32ccrc;
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Assert(record->xl_tot_len >=SizeOfXLogRecord);
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/* Calculate the CRC */
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INIT_CRC32C(crc);
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COMP_CRC32C(crc, ((char*)record)+SizeOfXLogRecord,record->xl_tot_len-SizeOfXLogRecord);

‎src/test/recovery/t/039_end_of_wal.pl‎

Lines changed: 13 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -281,6 +281,19 @@ sub advance_to_record_splitting_zone
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$log_size),
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"xl_tot_len short");
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# xl_tot_len in final position, not big enough to span into a new page but
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# also not eligible for regular record header validation
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emit_message($node, 0);
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$end_lsn = advance_to_record_splitting_zone($node);
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$node->stop('immediate');
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write_wal($node,$TLI,$end_lsn, build_record_header(1));
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$log_size =-s$node->logfile;
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$node->start;
292+
ok($node->log_contains(
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"invalid record length at .*: expected at least 24, got 1",$log_size
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),
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"xl_tot_len short at end-of-page");
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# Need more pages, but xl_prev check fails first.
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emit_message($node, 0);
286299
$end_lsn = advance_out_of_record_splitting_zone($node);

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