pgsql: Avoid double-free in vacuumlo error path.

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: pgsql-committers(at)lists(dot)postgresql(dot)org
Subject: pgsql: Avoid double-free in vacuumlo error path.
Date: 2019-03-24 19:13:39
Message-ID: E1h88Yt-0001r5-MI@gemulon.postgresql.org
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Avoid double-free in vacuumlo error path.

The code would do "PQclear(res)" twice if lo_unlink failed, evidently
due to careless thinking about how far out a "break" would break.
Remove the extra PQclear and adjust the loop logic so that we'll fall
out of both levels of loop after an error, as was clearly the intent.

Spotted by Coverity. I have no idea why it took this long to notice,
since the bug has been there since commit 67ccbb080. Accordingly,
back-patch to all supported branches.

Branch
------
REL9_6_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/9264888225ac4dabf399f06775073e14c38a87f7

Modified Files
--------------
contrib/vacuumlo/vacuumlo.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

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