From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42630) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eigQj-0002wz-CK for qemu-devel@nongnu.org; Mon, 05 Feb 2018 08:03:34 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eigQe-0006Y5-EU for qemu-devel@nongnu.org; Mon, 05 Feb 2018 08:03:29 -0500 Received: from mx1.redhat.com ([209.132.183.28]:54696) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eigQe-0006Xo-6f for qemu-devel@nongnu.org; Mon, 05 Feb 2018 08:03:24 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 743CC486CD for ; Mon, 5 Feb 2018 13:03:23 +0000 (UTC) References: <20180205114938.15784-1-berrange@redhat.com> <20180205114938.15784-4-berrange@redhat.com> From: Laszlo Ersek Message-ID: Date: Mon, 5 Feb 2018 14:03:14 +0100 MIME-Version: 1.0 In-Reply-To: <20180205114938.15784-4-berrange@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH 3/4] ui: check VNC audio frequency limit at time of reading from client List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "=?UTF-8?Q?Daniel_P._Berrang=c3=a9?=" , qemu-devel@nongnu.org Cc: Gerd Hoffmann On 02/05/18 12:49, Daniel P. Berrang=C3=A9 wrote: > The 'vs->as.freq' value is a signed integer, which is read from an > unsigned 32-bit int field on the wire. There is thus a risk of overflow > on 32-bit platforms. Move the frequency limit checking to be done at > time of read before casting to a signed integer. >=20 > Reported-by: Laszlo Ersek > Signed-off-by: Daniel P. Berrang=C3=A9 > --- > ui/vnc.c | 22 +++++++++++++--------- > 1 file changed, 13 insertions(+), 9 deletions(-) >=20 > diff --git a/ui/vnc.c b/ui/vnc.c > index e14e524764..79ac9eccde 100644 > --- a/ui/vnc.c > +++ b/ui/vnc.c > @@ -982,14 +982,7 @@ static void vnc_update_throttle_offset(VncState *v= s) > vs->client_width * vs->client_height * vs->client_pf.bytes_per= _pixel; > =20 > if (vs->audio_cap) { > - int freq =3D vs->as.freq; > - /* We don't limit freq when reading settings from client, so > - * it could be upto MAX_INT in size. 48khz is a sensible > - * upper bound for trustworthy clients */ > int bps; > - if (freq > 48000) { > - freq =3D 48000; > - } > switch (vs->as.fmt) { > default: > case AUD_FMT_U8: > @@ -1005,7 +998,7 @@ static void vnc_update_throttle_offset(VncState *v= s) > bps =3D 4; > break; > } > - offset +=3D freq * bps * vs->as.nchannels; > + offset +=3D vs->as.freq * bps * vs->as.nchannels; > } > =20 > /* Put a floor of 1MB on offset, so that if we have a large pendin= g > @@ -2279,6 +2272,7 @@ static int protocol_client_msg(VncState *vs, uint= 8_t *data, size_t len) > { > int i; > uint16_t limit; > + uint32_t freq; > VncDisplay *vd =3D vs->vd; > =20 > if (data[0] > 3) { > @@ -2398,7 +2392,17 @@ static int protocol_client_msg(VncState *vs, uin= t8_t *data, size_t len) > vnc_client_error(vs); > break; > } > - vs->as.freq =3D read_u32(data, 6); > + freq =3D read_u32(data, 6); > + /* No official limit for protocol, but 48khz is a sens= ible > + * upper bound for trustworthy clients, and this limit > + * protects calculations involving 'vs->as.freq' later= . > + */ > + if (freq > 48000) { > + VNC_DEBUG("Invalid audio frequency %u > 48000", fr= eq); > + vnc_client_error(vs); > + break; > + } > + vs->as.freq =3D freq; > break; > default: > VNC_DEBUG("Invalid audio message %d\n", read_u8(data, = 4)); >=20 Reviewed-by: Laszlo Ersek