Message-ID: <24d9dd82485fc058abddc31bd31a041926d7a905.camel@gmail.com>
Subject: Re: [PATCH v1 1/1] pstore/ram: Fix crash when setting number of
 cpus to an odd number
From:   Miko Larsson <mikoxyzzz@gmail.com>
To:     Weichen Chen <weichen.chen@mediatek.com>, yt.shen@mediatek.com,
        darren.chen@mediatek.com, keescook@chromium.org,
        tony.luck@intel.com, angelogioacchino.delregno@collabora.com,
        matthias.bgg@gmail.com, gpiccoli@igalia.com,
        linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Fri, 24 Feb 2023 08:05:01 +0100
In-Reply-To: <20230224023632.6840-1-weichen.chen@mediatek.com>
References: <20230224023632.6840-1-weichen.chen@mediatek.com>
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On Fri, 2023-02-24 at 10:36 +0800, Weichen Chen wrote:
> When the number of cpu cores is adjusted to 7 or other odd numbers,
> the zone size will become an odd number.
> The address of the zone will become:
> =C2=A0=C2=A0=C2=A0 addr of zone0 =3D BASE
> =C2=A0=C2=A0=C2=A0 addr of zone1 =3D BASE + zone_size
> =C2=A0=C2=A0=C2=A0 addr of zone2 =3D BASE + zone_size*2
> =C2=A0=C2=A0=C2=A0 ...
> The address of zone1/3/5/7 will be mapped to non-alignment va.
> Eventually crashes will occur when accessing these va.
>=20
> So, use ALIGN_DOWN() to make sure the zone size is even
> to avoid this bug.
>=20
> Signed-off-by: Weichen Chen <weichen.chen@mediatek.com>
> ---
> =C2=A0fs/pstore/ram.c | 1 +
> =C2=A01 file changed, 1 insertion(+)
>=20
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index ade66dbe5f39..fc57ac97e506 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -528,6 +528,7 @@ static int ramoops_init_przs(const char *name,
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0}
> =C2=A0
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0zone_sz =3D mem_sz / *cnt=
;
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0zone_sz =3D ALIGN_DOWN(zone_sz=
, 2);
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (!zone_sz) {
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0dev_err(dev, "%s zone size =3D=3D 0\n", name);
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0goto fail;

Might want to Cc this to the stable mailing list.
--=20
~miko