pgsql: Fix assorted integer-overflow hazards in varbit.c.

Fix assorted integer-overflow hazards in varbit.c.

bitshiftright() and bitshiftleft() would recursively call each other
infinitely if the user passed INT_MIN for the shift amount, due to integer
overflow in negating the shift amount. To fix, clamp to -VARBITMAXLEN.
That doesn't change the results since any shift distance larger than the
input bit string's length produces an all-zeroes result.

Also fix some places that seemed inadequately paranoid about input typmods
exceeding VARBITMAXLEN. While a typmod accepted by anybit_typmodin() will
certainly be much less than that, at least some of these spots are
reachable with user-chosen integer values.

Andreas Seltenreich and Tom Lane

Discussion: <87d1j2zqtz(dot)fsf(at)credativ(dot)de>

Branch
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REL9_6_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/4338ac8e78e95dcc327e86fc9944bdae8c551c27

Modified Files
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src/backend/utils/adt/varbit.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)