Thread: pgsql: Ensure maxlen is at leat 1 in dict_int

Ensure maxlen is at leat 1 in dict_int

The dict_int text search dictionary template accepts maxlen parameter,
which is then used to cap the length of input strings. The value was
not properly checked, and the code simply does

    txt[d->maxlen] = '\0';

to insert a terminator, leading to segfaults with negative values.

This commit simply rejects values less than 1. The issue was there since
dct_int was introduced in 9.3, so backpatch all the way back to 9.4
which is the oldest supported version.

Reported-by: cili
Discussion: https://postgr.es/m/16144-a36a5bef7657047d@postgresql.org
Backpatch-through: 9.4

Branch
------
REL_12_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/a8a8c6b296406bbf30948768939c08457bd468a4

Modified Files
--------------
contrib/dict_int/dict_int.c            | 5 +++++
contrib/dict_int/expected/dict_int.out | 2 ++
contrib/dict_int/sql/dict_int.sql      | 2 ++
3 files changed, 9 insertions(+)