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Don't get confused if a WAL partial record header has xl_tot_len == 0.

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If a WAL record header was split across pages, but xl_tot_len was 0, we
would get confused and conclude that we had already read the whole record,
and proceed to CRC check it. That can lead to a crash in RecordIsValid(),
which isn't careful to not read beyond end-of-record, as defined by
xl_tot_len.

Add an explicit sanity check for xl_tot_len <= SizeOfXlogRecord. Also,
make RecordIsValid() more robust by checking in each step that it doesn't
try to access memory beyond end of record, even if a length field in the
record's or a backup block's header is bogus.

Per report and analysis by Tom Lane.
This commit is contained in:
Heikki Linnakangas 2012-08-20 19:51:42 +03:00
parent 9b2a237cee
commit 51fed14d73
1 changed files with 36 additions and 2 deletions
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38
src/backend/access/transam/xlog.c
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@ -3707,8 +3707,17 @@ RecordIsValid(XLogRecord *record, XLogRecPtr recptr, int emode)
uint32 len = record->xl_len;
BkpBlock bkpb;
char *blk;
char *recend = (char *) record + record->xl_tot_len;
/* First the rmgr data */
if (XLogRecGetData(record) + len > recend)
{
/* ValidXLogRecordHeader() should've caught this already... */
ereport(emode_for_corrupt_record(emode, recptr),
(errmsg("invalid record length at %X/%X",
(uint32) (recptr >> 32), (uint32) recptr)));
return false;
}
INIT_CRC32(crc);
COMP_CRC32(crc, XLogRecGetData(record), len);
@ -3721,7 +3730,15 @@ RecordIsValid(XLogRecord *record, XLogRecPtr recptr, int emode)
if (!(record->xl_info & XLR_SET_BKP_BLOCK(i)))
continue;
if (blk + sizeof(BkpBlock) > recend)
{
ereport(emode_for_corrupt_record(emode, recptr),
(errmsg("incorrect backup block size in record at %X/%X",
(uint32) (recptr >> 32), (uint32) recptr)));
return false;
}
memcpy(&bkpb, blk, sizeof(BkpBlock));
if (bkpb.hole_offset + bkpb.hole_length > BLCKSZ)
{
ereport(emode_for_corrupt_record(emode, recptr),
@ -3730,6 +3747,14 @@ RecordIsValid(XLogRecord *record, XLogRecPtr recptr, int emode)
return false;
}
blen = sizeof(BkpBlock) + BLCKSZ - bkpb.hole_length;
if (blk + blen > recend)
{
ereport(emode_for_corrupt_record(emode, recptr),
(errmsg("invalid backup block size in record at %X/%X",
(uint32) (recptr >> 32), (uint32) recptr)));
return false;
}
COMP_CRC32(crc, blk, blen);
blk += blen;
}
@ -3879,8 +3904,8 @@ retry:
/*
* If the whole record header is on this page, validate it immediately.
* Otherwise validate it after reading the rest of the header from next
* page.
* Otherwise only do a basic sanity check on xl_tot_len, and validate the
* rest of the header after reading it from the next page.
*/
if (targetRecOff <= XLOG_BLCKSZ - SizeOfXLogRecord)
{
@ -3889,7 +3914,16 @@ retry:
gotheader = true;
}
else
{
if (total_len < SizeOfXLogRecord)
{
ereport(emode_for_corrupt_record(emode, *RecPtr),
(errmsg("invalid record length at %X/%X",
(uint32) ((*RecPtr) >> 32), (uint32) *RecPtr)));
goto next_record_is_invalid;
}
gotheader = false;
}
/*
* Allocate or enlarge readRecordBuf as needed. To avoid useless small