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commit df1ce4d4a224df037b8cbc37384f5b5f9a2dab4a Author: Thomas Munro <[email protected]> AuthorDate: Tue Sep 26 09:07:26 2023 +1300 Fix edge-case for xl_tot_len broken by bae868ca. bae868ca removed a check that was still needed. If you had an xl_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 perform the CRC check using a bogus large length. Because of arbitrary coding differences between the CRC implementations on different platforms, nothing very bad happened on common modern systems. On systems using the _sb8.c fallback we could segfault. Restore that check, add a new assertion and supply a test for that case. Back-patch to 12, like bae868ca. Tested-by: Tom Lane <[email protected]> Tested-by: Alexander Lakhin <[email protected]> Discussion: https://postgr.es/m/CA%2BhUKGLCkTT7zYjzOxuLGahBdQ%3DMcF%3Dz5ZvrjSOnW4EDhVjT-g%40mail.gmail.com --- src/backend/access/transam/xlogreader.c | 11 +++++++++++ src/test/recovery/t/039_end_of_wal.pl | 13 +++++++++++++ 2 files changed, 24 insertions(+) diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c index 67e6b9cf717..af5e8508bf1 100644 --- a/src/backend/access/transam/xlogreader.c +++ b/src/backend/access/transam/xlogreader.c @@ -388,6 +388,15 @@ restart: } else { + /* There may be no next page if it's too small. */ + if (total_len < SizeOfXLogRecord) + { + report_invalid_record(state, + "invalid record length at %X/%X: wanted %u, got %u", + LSN_FORMAT_ARGS(RecPtr), + (uint32) SizeOfXLogRecord, total_len); + goto err; + } /* We'll validate the header once we have the next page. */ gotheader = false; } @@ -800,6 +809,8 @@ ValidXLogRecord(XLogReaderState *state, XLogRecord *record, XLogRecPtr recptr) { pg_crc32c crc; + Assert(record->xl_tot_len >= SizeOfXLogRecord); + /* Calculate the CRC */ INIT_CRC32C(crc); COMP_CRC32C(crc, ((char *) record) + SizeOfXLogRecord, record->xl_tot_len - SizeOfXLogRecord); diff --git a/src/test/recovery/t/039_end_of_wal.pl b/src/test/recovery/t/039_end_of_wal.pl index 1eb65c07654..1d1d883be6a 100644 --- a/src/test/recovery/t/039_end_of_wal.pl +++ b/src/test/recovery/t/039_end_of_wal.pl @@ -287,6 +287,19 @@ ok( $node->log_contains( $log_size), "xl_tot_len short"); +# xl_tot_len in final position, not big enough to span into a new page but +# also not eligible for regular record header validation +emit_message($node, 0); +$end_lsn = advance_to_record_splitting_zone($node); +$node->stop('immediate'); +write_wal($node, $TLI, $end_lsn, build_record_header(1)); +$log_size = -s $node->logfile; +$node->start; +ok( $node->log_contains( + "invalid record length at .*: wanted 24, got 1", $log_size + ), + "xl_tot_len short at end-of-page"); + # Need more pages, but xl_prev check fails first. emit_message($node, 0); $end_lsn = advance_out_of_record_splitting_zone($node); --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
