pgsql: Avoid possible overflow with ltsGetFreeBlock() in logtape.c

Avoid possible overflow with ltsGetFreeBlock() in logtape.c

nFreeBlocks, defined as a long, stores the number of free blocks in a
logical tape. ltsGetFreeBlock() has been using an int to store the
value of nFreeBlocks, which could lead to overflows on platforms where
long and int are not the same size (in short everything except Windows
where long is 4 bytes).

The problematic intermediate variable is switched to be a long instead
of an int.

Issue introduced by c02fdc9223015, so backpatch down to 13.

Author: Ranier vilela
Reviewed-by: Peter Geoghegan, David Rowley
Discussion: https://postgr.es/m/CAEudQApLDWCBR_xmwNjGBrDo+f+S4E87x3s7-+hoaKqYdtC4JQ@mail.gmail.com
Backpatch-through: 13

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/52c6c0f19693367d542d1286c978a713ffcedd3a

Modified Files
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src/backend/utils/sort/logtape.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)