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Subject: Re: [PATCH 8/8] xen/hvc: replace BUG_ON() with negative return value
To:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        xen-devel@lists.xenproject.org, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>
References: <20210513100302.22027-1-jgross@suse.com>
 <20210513100302.22027-9-jgross@suse.com>
 <6da4cc91-ccde-fce8-707c-e7544783c2fa@csgroup.eu>
From:   Juergen Gross <jgross@suse.com>
Message-ID: <e62b12e7-6dbe-3d26-2196-9cbc2c0d4160@suse.com>
Date:   Thu, 13 May 2021 12:20:35 +0200
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From: Juergen Gross <jgross@suse.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>,
 xen-devel@lists.xenproject.org, linuxppc-dev@lists.ozlabs.org,
 linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 Jiri Slaby <jirislaby@kernel.org>
Message-ID: <e62b12e7-6dbe-3d26-2196-9cbc2c0d4160@suse.com>
Subject: Re: [PATCH 8/8] xen/hvc: replace BUG_ON() with negative return value
References: <20210513100302.22027-1-jgross@suse.com>
 <20210513100302.22027-9-jgross@suse.com>
 <6da4cc91-ccde-fce8-707c-e7544783c2fa@csgroup.eu>
In-Reply-To: <6da4cc91-ccde-fce8-707c-e7544783c2fa@csgroup.eu>

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On 13.05.21 12:16, Christophe Leroy wrote:
>=20
>=20
> Le 13/05/2021 =C3=A0 12:03, Juergen Gross a =C3=A9crit=C2=A0:
>> Xen frontends shouldn't BUG() in case of illegal data received from
>> their backends. So replace the BUG_ON()s when reading illegal data fro=
m
>> the ring page with negative return values.
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> ---
>> =C2=A0 drivers/tty/hvc/hvc_xen.c | 15 +++++++++++++--
>> =C2=A0 1 file changed, 13 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
>> index 92c9a476defc..30d7ffb1e04c 100644
>> --- a/drivers/tty/hvc/hvc_xen.c
>> +++ b/drivers/tty/hvc/hvc_xen.c
>> @@ -86,6 +86,11 @@ static int __write_console(struct xencons_info=20
>> *xencons,
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 cons =3D intf->out_cons;
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 prod =3D intf->out_prod;
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 mb();=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* update queue values before going on */
>> +
>> +=C2=A0=C2=A0=C2=A0 if (WARN_ONCE((prod - cons) > sizeof(intf->out),
>> +=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 "Illegal ring page indices"))
>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return -EINVAL;
>> +
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 BUG_ON((prod - cons) > sizeof(intf->out=
));
>=20
> Why keep the BUG_ON() ?

Oh, failed to delete it. Thanks for noticing.


Juergen

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