pgsql: Fix PQsetvalue() to avoid possible crash when adding a new tuple

Fix PQsetvalue() to avoid possible crash when adding a new tuple.

PQsetvalue unnecessarily duplicated the logic in pqAddTuple, and didn't
duplicate it exactly either --- pqAddTuple does not care what is in the
tuple-pointer array positions beyond the last valid entry, whereas the
code in PQsetvalue assumed such positions would contain NULL. This led
to possible crashes if PQsetvalue was applied to a PGresult that had
previously been enlarged with pqAddTuple, for instance one built from a
server query. Fix by relying on pqAddTuple instead of duplicating logic,
and not assuming anything about the contents of res->tuples[res->ntups].

Back-patch to 8.4, where PQsetvalue was introduced.

Andrew Chernow

Branch
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REL9_1_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/64207122a241282189451fdcbab3f5e2a6e1e1b1

Modified Files
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src/interfaces/libpq/fe-exec.c | 27 ++++-----------------------
1 files changed, 4 insertions(+), 23 deletions(-)