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pgsql: Don't get confused if a WAL partial record header hasxl_tot_len

From: Heikki Linnakangas <heikki(dot)linnakangas(at)iki(dot)fi>
To: pgsql-committers(at)postgresql(dot)org
Subject: pgsql: Don't get confused if a WAL partial record header hasxl_tot_len
Date: 2012-08-20 16:59:15
Message-ID: E1T3VJr-0000rX-7H@gemulon.postgresql.org (view raw or flat)
Thread:
Lists: pgsql-committers
Don't get confused if a WAL partial record header has xl_tot_len == 0.

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.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/51fed14d73ed3acd2282b531fb1396877e44e86a

Modified Files
--------------
src/backend/access/transam/xlog.c |   38 +++++++++++++++++++++++++++++++++++-
1 files changed, 36 insertions(+), 2 deletions(-)

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