Horton

Re: glibc qsort() vulnerability

Mats Kindahl <mats@timescale.com>

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From: Mats Kindahl <mats@timescale.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Nathan Bossart <nathandbossart@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2024-02-07T09:09:58Z
Lists: pgsql-hackers

Commits

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

  1. Use new overflow-safe integer comparison functions.

  2. Introduce overflow-safe integer comparison functions.

  3. Replace calls to pg_qsort() with the qsort() macro.

  4. Switch over to using our own qsort() all the time, as has been proposed

On Tue, Feb 6, 2024 at 9:56 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:

> Nathan Bossart <nathandbossart@gmail.com> writes:
> > Even if the glibc issue doesn't apply to Postgres, I'm tempted to suggest
> > that we make it project policy that comparison functions must be
> > transitive.  There might be no real issues today, but if we write all
> > comparison functions the way Mats is suggesting, it should be easier to
> > reason about overflow risks.
>
> A comparison routine that is not is probably broken, agreed.
> I didn't look through the details of the patch --- I was more
> curious whether we had a version of the qsort bug, because
> if we do, we should fix that too.
>

The patch basically removes the risk of overflow in three routines and just
returns -1, 0, or 1, and adds a comment in one.

The routines modified do a subtraction of int:s and return that, which can
cause an overflow. This method is used for some int16 as well but since
standard conversions in C will perform the arithmetics in "int" precision,
this cannot overflow, so added a comment there. It might still be a good
idea to follow the same pattern for the int16 routines, but since there is
no bug there, I did not add them to the patch.

Best wishes,
Mats Kindahl



>
>                         regards, tom lane
>