linux-kernel - [PATCH 5/5] drm/dsc: Prevent negative BPG offsets from shadowing adjacent bitfields

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20221001190807.358691-6-marijn.suijten@somainline.org>
Date:   Sat,  1 Oct 2022 21:08:07 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     phone-devel@...r.kernel.org, Rob Clark <robdclark@...il.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Vinod Koul <vkoul@...nel.org>
Cc:     ~postmarketos/upstreaming@...ts.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Alex Deucher <alexander.deucher@....com>,
        Douglas Anderson <dianders@...omium.org>,
        Vladimir Lypak <vladimir.lypak@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        Lyude Paul <lyude@...hat.com>
Subject: [PATCH 5/5] drm/dsc: Prevent negative BPG offsets from shadowing adjacent bitfields

msm's dsi_host specifies negative BPG offsets which fill the full 8 bits
of a char thanks to two's complement: this however results in those bits
bleeding into the next parameter when the field is only expected to
contain 6-bit wide values.
As a consequence random slices appear corrupted on-screen (tested on a
Sony Tama Akatsuki device with sdm845).

Use AND operators to limit all values that constitute the RC Range
parameter fields to their expected size.

Fixes: b9080324d6ca ("drm/msm/dsi: add support for dsc data")
Signed-off-by: Marijn Suijten <marijn.suijten@...ainline.org>
---
 drivers/gpu/drm/display/drm_dsc_helper.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_dsc_helper.c b/drivers/gpu/drm/display/drm_dsc_helper.c
index c869c6e51e2b..2e7ef242685d 100644
--- a/drivers/gpu/drm/display/drm_dsc_helper.c
+++ b/drivers/gpu/drm/display/drm_dsc_helper.c
@@ -243,11 +243,11 @@ void drm_dsc_pps_payload_pack(struct drm_dsc_picture_parameter_set *pps_payload,
 	 */
 	for (i = 0; i < DSC_NUM_BUF_RANGES; i++) {
 		pps_payload->rc_range_parameters[i] =
-			cpu_to_be16((dsc_cfg->rc_range_params[i].range_min_qp <<
+			cpu_to_be16(((dsc_cfg->rc_range_params[i].range_min_qp & 0x1f) <<
 				     DSC_PPS_RC_RANGE_MINQP_SHIFT) |
-				    (dsc_cfg->rc_range_params[i].range_max_qp <<
+				    ((dsc_cfg->rc_range_params[i].range_max_qp & 0x1f) <<
 				     DSC_PPS_RC_RANGE_MAXQP_SHIFT) |
-				    (dsc_cfg->rc_range_params[i].range_bpg_offset));
+				    (dsc_cfg->rc_range_params[i].range_bpg_offset & 0x3f));
 	}
 
 	/* PPS 88 */
-- 
2.37.3