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help / color / mirror / Atom feedFrom: Nathan Bossart <nathandbossart@gmail.com>
To: Mats Kindahl <mats@timescale.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andres Freund <andres@anarazel.de>
Cc: Thomas Munro <thomas.munro@gmail.com>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: pgsql-hackers@lists.postgresql.org
Subject: Re: glibc qsort() vulnerability
Date: Fri, 9 Feb 2024 10:24:33 -0600
Message-ID: <20240209162433.GA663211@nathanxps13> (raw)
In-Reply-To: <CA+14425sEcy-KzCE1ztpO=XrHZ5u_5tR2UNsw6874dVbAShpzQ@mail.gmail.com>
References: <CA+hUKGLbC4O56rtFM69Tx6StT3PcVio9K2GisjZp=z6O20Q3sw@mail.gmail.com>
<CA+hUKGJaOM5ULeXboxV+fGkU-pYHotL5A10hYxdu8_kwRcVEgQ@mail.gmail.com>
<20240208025620.GC445153@nathanxps13>
<CA+14424k0MbdkJuSSLrr1==PYK+oL5Gtq7siTsMgCs+KcCrEvA@mail.gmail.com>
<20240208183835.GA503311@nathanxps13>
<1074897.1707417842@sss.pgh.pa.us>
<20240208195954.vlpoii4ftoow2of4@awork3.anarazel.de>
<20240208200737.GA504276@nathanxps13>
<1242426.1707424769@sss.pgh.pa.us>
<CA+14425sEcy-KzCE1ztpO=XrHZ5u_5tR2UNsw6874dVbAShpzQ@mail.gmail.com>
On Fri, Feb 09, 2024 at 08:52:26AM +0100, Mats Kindahl wrote:
> Here is a new version introducing pg_cmp_s32 and friends and use them
> instead of the INT_CMP macro introduced before. It also moves the
> definitions to common/int.h and adds that as an include to all locations
> using these functions.
Thanks for the new version of the patch.
> Note that for integers with sizes less than sizeof(int), C standard
> conversions will convert the values to "int" before doing the arithmetic,
> so no casting is *necessary*. I did not force the 16-bit functions to
> return -1 or 1 and have updated the comment accordingly.
It might not be necessary, but this is one of those places where I would
add casting anyway to make it abundantly clear what we are expecting to
happen and why it is safe.
> The types "int" and "size_t" are treated as s32 and u32 respectively since
> that seems to be the case for most of the code, even if strictly not
> correct (size_t can be an unsigned long int for some architecture).
Why is it safe to do this?
> - return ((const SPLITCOST *) a)->cost - ((const SPLITCOST *) b)->cost;
> + return INT_CMP(((const SPLITCOST *) a)->cost, ((const SPLITCOST *) b)->cost);
The patch still contains several calls to INT_CMP.
> +/*------------------------------------------------------------------------
> + * Comparison routines for integers
> + *------------------------------------------------------------------------
> + */
I'd suggest separating this part out to a 0001 patch to make it easier to
review. The 0002 patch could take care of converting the existing qsort
comparators.
> +static inline int
> +pg_cmp_s16(int16 a, int16 b)
> +{
> + return a - b;
> +}
> +
> +static inline int
> +pg_cmp_u16(uint16 a, uint16 b)
> +{
> + return a - b;
> +}
> +
> +static inline int
> +pg_cmp_s32(int32 a, int32 b)
> +{
> + return (a > b) - (a < b);
> +}
> +
> +static inline int
> +pg_cmp_u32(uint32 a, uint32 b)
> +{
> + return (a > b) - (a < b);
> +}
> +
> +static inline int
> +pg_cmp_s64(int64 a, int64 b)
> +{
> + return (a > b) - (a < b);
> +}
> +
> +static inline int
> +pg_cmp_u64(uint64 a, uint64 b)
> +{
> + return (a > b) - (a < b);
> +}
As suggested above, IMHO we should be rather liberal with the casting to
ensure it is abundantly clear what is happening here.
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
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To: pgsql-hackers@postgresql.org
Cc: nathandbossart@gmail.com, mats@timescale.com, tgl@sss.pgh.pa.us, andres@anarazel.de, thomas.munro@gmail.com, hlinnaka@iki.fi, pgsql-hackers@lists.postgresql.org
Subject: Re: glibc qsort() vulnerability
In-Reply-To: <20240209162433.GA663211@nathanxps13>
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