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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id 8sm13774838pjs.39.2022.02.04.17.41.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Feb 2022 17:41:13 -0800 (PST) Date: Fri, 4 Feb 2022 17:41:12 -0800 From: Kees Cook To: Maarten Lankhorst , David Airlie , Daniel Vetter Cc: Maxime Ripard , Thomas Zimmermann , dri-devel@lists.freedesktop.org, Jani Nikula , Thierry Reding , Jonathan Hunter , Philipp Zabel , Lyude Paul , linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] drm/dp: Remove common Post Cursor2 register handling Message-ID: <202202041740.F368F91F5@keescook> References: <20220105173507.2420910-1-keescook@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220105173507.2420910-1-keescook@chromium.org> Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org Ping, This is a OOB read fix. Can someone please pick this up? -Kees On Wed, Jan 05, 2022 at 09:35:07AM -0800, Kees Cook wrote: > The link_status array was not large enough to read the Adjust Request > Post Cursor2 register, so remove the common helper function to avoid > an OOB read, found with a -Warray-bounds build: > > drivers/gpu/drm/drm_dp_helper.c: In function 'drm_dp_get_adjust_request_post_cursor': > drivers/gpu/drm/drm_dp_helper.c:59:27: error: array subscript 10 is outside array bounds of 'const u8[6]' {aka 'const unsigned char[6]'} [-Werror=array-bounds] > 59 | return link_status[r - DP_LANE0_1_STATUS]; > | ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~ > drivers/gpu/drm/drm_dp_helper.c:147:51: note: while referencing 'link_status' > 147 | u8 drm_dp_get_adjust_request_post_cursor(const u8 link_status[DP_LINK_STATUS_SIZE], > | ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Replace the only user of the helper with an open-coded fetch and decode, > similar to drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c. > > Fixes: 79465e0ffeb9 ("drm/dp: Add helper to get post-cursor adjustments") > Cc: Maarten Lankhorst > Cc: Maxime Ripard > Cc: Thomas Zimmermann > Cc: David Airlie > Cc: Daniel Vetter > Cc: dri-devel@lists.freedesktop.org > Signed-off-by: Kees Cook > --- > This is the alternative to: > https://lore.kernel.org/lkml/20211203084354.3105253-1-keescook@chromium.org/ > --- > drivers/gpu/drm/drm_dp_helper.c | 10 ---------- > drivers/gpu/drm/tegra/dp.c | 11 ++++++++++- > include/drm/drm_dp_helper.h | 2 -- > 3 files changed, 10 insertions(+), 13 deletions(-) > > diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c > index 23f9073bc473..c9528aa62c9c 100644 > --- a/drivers/gpu/drm/drm_dp_helper.c > +++ b/drivers/gpu/drm/drm_dp_helper.c > @@ -144,16 +144,6 @@ u8 drm_dp_get_adjust_tx_ffe_preset(const u8 link_status[DP_LINK_STATUS_SIZE], > } > EXPORT_SYMBOL(drm_dp_get_adjust_tx_ffe_preset); > > -u8 drm_dp_get_adjust_request_post_cursor(const u8 link_status[DP_LINK_STATUS_SIZE], > - unsigned int lane) > -{ > - unsigned int offset = DP_ADJUST_REQUEST_POST_CURSOR2; > - u8 value = dp_link_status(link_status, offset); > - > - return (value >> (lane << 1)) & 0x3; > -} > -EXPORT_SYMBOL(drm_dp_get_adjust_request_post_cursor); > - > static int __8b10b_clock_recovery_delay_us(const struct drm_dp_aux *aux, u8 rd_interval) > { > if (rd_interval > 4) > diff --git a/drivers/gpu/drm/tegra/dp.c b/drivers/gpu/drm/tegra/dp.c > index 70dfb7d1dec5..f5535eb04c6b 100644 > --- a/drivers/gpu/drm/tegra/dp.c > +++ b/drivers/gpu/drm/tegra/dp.c > @@ -549,6 +549,15 @@ static void drm_dp_link_get_adjustments(struct drm_dp_link *link, > { > struct drm_dp_link_train_set *adjust = &link->train.adjust; > unsigned int i; > + u8 post_cursor; > + int err; > + > + err = drm_dp_dpcd_read(link->aux, DP_ADJUST_REQUEST_POST_CURSOR2, > + &post_cursor, sizeof(post_cursor)); > + if (err < 0) { > + DRM_ERROR("failed to read post_cursor2: %d\n", err); > + post_cursor = 0; > + } > > for (i = 0; i < link->lanes; i++) { > adjust->voltage_swing[i] = > @@ -560,7 +569,7 @@ static void drm_dp_link_get_adjustments(struct drm_dp_link *link, > DP_TRAIN_PRE_EMPHASIS_SHIFT; > > adjust->post_cursor[i] = > - drm_dp_get_adjust_request_post_cursor(status, i); > + (post_cursor >> (i << 1)) & 0x3; > } > } > > diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h > index 472dac376284..fdf3cf6ccc02 100644 > --- a/include/drm/drm_dp_helper.h > +++ b/include/drm/drm_dp_helper.h > @@ -1528,8 +1528,6 @@ u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SI > int lane); > u8 drm_dp_get_adjust_tx_ffe_preset(const u8 link_status[DP_LINK_STATUS_SIZE], > int lane); > -u8 drm_dp_get_adjust_request_post_cursor(const u8 link_status[DP_LINK_STATUS_SIZE], > - unsigned int lane); > > #define DP_BRANCH_OUI_HEADER_SIZE 0xc > #define DP_RECEIVER_CAP_SIZE 0xf > -- > 2.30.2 > -- Kees Cook