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Date:      Tue, 3 Jun 2025 00:19:55 +0000
From:      Shawn Webb <shawn.webb@hardenedbsd.org>
To:        Robert Clausecker <fuz@freebsd.org>
Cc:        src-committers@freebsd.org, dev-commits-src-all@freebsd.org,  dev-commits-src-main@freebsd.org
Subject:   Re: git: e698e4a53773 - main - lib/libmd: disable SHA1 AVX2 kernel
Message-ID:  <qyz7fzuu2dtxz4xaazr6c45nkdm7xlm7zpvx3sr4czv2n2ognr@h3yflsswnytm>
In-Reply-To: <iswwxq67opsuxidiehxizr7yg6em2obolcw2qx5d5rb2op5xij@wvozbns6esrt>
References:  <202506022333.552NX1uN061534@gitrepo.freebsd.org> <iswwxq67opsuxidiehxizr7yg6em2obolcw2qx5d5rb2op5xij@wvozbns6esrt>

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Subject: Re: git: e698e4a53773 - main - lib/libmd: disable SHA1 AVX2 kernel
MIME-Version: 1.0

On Tue, Jun 03, 2025 at 12:17:26AM +0000, Shawn Webb wrote:
> On Mon, Jun 02, 2025 at 11:33:01PM +0000, Robert Clausecker wrote:
> > The branch main has been updated by fuz:
> >=20
> > URL: https://cgit.FreeBSD.org/src/commit/?id=3De698e4a537736f6a7dd9a386=
e00997d7fb08e83f
> >=20
> > commit e698e4a537736f6a7dd9a386e00997d7fb08e83f
> > Author:     Robert Clausecker <fuz@FreeBSD.org>
> > AuthorDate: 2025-06-02 22:54:32 +0000
> > Commit:     Robert Clausecker <fuz@FreeBSD.org>
> > CommitDate: 2025-06-02 23:27:00 +0000
> >=20
> >     lib/libmd: disable SHA1 AVX2 kernel
> >    =20
> >     Seems like there is a bug lurking somewhere in the code.  This was =
not
> >     caught during my testing.  Disable the affected kernel for now whil=
e I
> >     figure out what is wrong with it.
> >    =20
> >     To reproduce, run
> >    =20
> >         jot -s '' -b 'a' -n 1000000 | sha1
> >    =20
> >     This should yield 34aa973cd4c4daa4f61eeb2bdbad27316534016f, but giv=
es
> >     fe161a71d7941e3d63a9cacadc4f20716a721944 with the broken code.  Onl=
y the
> >     amd64/avx2 kernel is affected, the others seem to operate correctly.
>=20
> Out of curiosity, how would one best determine whether they're
> affected? Would it be a part of the CPU features shown in
> /var/run/dmesg.boot?

Nevermind, running your reproducer above is sufficient. And, it
appears that one of my Intel laptops is affected. I do see the
following line in /var/run/dmesg.boot:

Structured Extended Features=3D0x1407a9<FSGSBASE,BMI1,AVX2,SMEP,BMI2,ERMS,I=
NVPCID,RDSEED,SMAP>

Sorry for the noise.

--=20
Shawn Webb
Cofounder / Security Engineer
HardenedBSD

Signal Username:  shawn_webb.74
Tor-ified Signal: +1 303-901-1600 / shawn_webb_opsec.50
https://git.hardenedbsd.org/hardenedbsd/pubkeys/-/raw/master/Shawn_Webb/03A=
4CBEBB82EA5A67D9F3853FF2E67A277F8E1FA.pub.asc

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