Plug-in coverage hole for pglz_decompress()

Michael Paquier <michael@paquier.xyz>

From: Michael Paquier <michael@paquier.xyz>

To: Postgres hackers <pgsql-hackers@lists.postgresql.org>

Cc: Andrew Dunstan <andrew@dunslane.net>

Date: 2026-05-11T06:35:50Z

Lists: pgsql-hackers

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Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Add more tests for corrupted data with pglz_decompress()
- 5c00f4e2e3bc 14 (unreleased) landed
- f4ba78081895 15 (unreleased) landed
- 5f12d86dd762 16 (unreleased) landed
- 54eeefaedbee 17 (unreleased) landed
- 89192080f0a9 18 (unreleased) landed
- 900c07b854a7 19 (unreleased) landed

Attachments

0001-Add-more-tests-for-corrupted-data-in-pglz_decompress.patch (text/plain) patch 0001

Hi all,
(Andrew in CC, in case.)

While doing a post-commit review of 67d318e70402, I have noticed the
following coverage hole in pglz_decompress(), where a failure of this
check is not covered, see also [1]:
    if (unlikely(off == 0 ||
                 off > (dp - (unsigned char *) dest)))
        return -1;

This can be triggered easily with the two following sequences in the
regression tests:
SELECT test_pglz_decompress('\x011001'::bytea, 1024, true);
SELECT test_pglz_decompress('\x010300'::bytea, 1024, true);

It's unfortunately too late for this round of minor releases, but I'd
like to fix this hole once the next minor versions are tagged, down to
v14.  If there are any objections or comments, feel free.  Mea culpa.

Thanks,

[1]: https://coverage.postgresql.org/src/common/pg_lzcompress.c.gcov.html
--
Michael