pgsql: Fix datalen calculation in tsvectorrecv(). - Mailing list pgsql-committers

From Tom Lane
Subject pgsql: Fix datalen calculation in tsvectorrecv().
Date
Msg-id E1qn06k-0070kl-ME@gemulon.postgresql.org
Whole thread Raw
List pgsql-committers
Fix datalen calculation in tsvectorrecv().

After receiving position data for a lexeme, tsvectorrecv()
advanced its "datalen" value by (npos+1)*sizeof(WordEntry)
where the correct calculation is (npos+1)*sizeof(WordEntryPos).
This accidentally failed to render the constructed tsvector
invalid, but it did result in leaving some wasted space
approximately equal to the space consumed by the position data.
That could have several bad effects:

* Disk space is wasted if the received tsvector is stored into a
  table as-is.

* A legal tsvector could get rejected with "maximum total lexeme
  length exceeded" if the extra space pushes it over the MAXSTRPOS
  limit.

* In edge cases, the finished tsvector could be assigned a length
  larger than the allocated size of its palloc chunk, conceivably
  leading to SIGSEGV when the tsvector gets copied somewhere else.
  The odds of a field failure of this sort seem low, though valgrind
  testing could probably have found this.

While we're here, let's express the calculation as
"sizeof(uint16) + npos * sizeof(WordEntryPos)" to avoid the type
pun implicit in the "npos + 1" formulation.  It's not wrong
given that WordEntryPos had better be 2 bytes to avoid padding
problems, but it seems clearer this way.

Report and patch by Denis Erokhin.  Back-patch to all supported
versions.

Discussion: https://postgr.es/m/009801d9f2d9$f29730c0$d7c59240$@datagile.ru

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/5b7b3824648d6324f649bc74713a6b35e53b91ac

Modified Files
--------------
src/backend/utils/adt/tsvector.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)


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