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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id my6-20020a17090b4c8600b001bc2cb011dasm705551pjb.4.2022.02.24.19.56.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Feb 2022 19:56:14 -0800 (PST) From: Kees Cook To: Daniel Vetter Cc: Kees Cook , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , dri-devel@lists.freedesktop.org, "Gustavo A . R . Silva" , Jani Nikula , Thierry Reding , Jonathan Hunter , Lyude Paul , =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= , Dave Airlie , Douglas Anderson , Ankit Nautiyal , Uma Shankar , Philipp Zabel , linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v3 2/2] drm/dp: Fix OOB read when handling Post Cursor2 register Date: Thu, 24 Feb 2022 19:56:10 -0800 Message-Id: <20220225035610.2552144-3-keescook@chromium.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220225035610.2552144-1-keescook@chromium.org> References: <20220225035610.2552144-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4091; h=from:subject; bh=96sk9Gtx/XNCiooctnCaqAKLVeawEGKb7AZz4nCMFf0=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBiGFNadg22VDVgjy8AQWiUERRf01Zq/MODlSMQoZ58 a8tOe/eJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYhhTWgAKCRCJcvTf3G3AJr2MEA CBjU4bY3VxDS3wV7gdhWpz4b/0P9Ujgue2yyAHPN90Srm5SEbd9jMDRfp9H3dMTE6A7BySPc4o4gCR H8DpGL5CHRY0FwK8TG4Cr5Zlzz9LxG6uR1SmCoPMKTL/XffQmUhYksEoIu/3dEgJZ7eoM+vpJFskuW 1T7Rcvu7jZ67Fx9sx6UfydjkuT6ETIT2gXIcDQXoHV8yCTYlmeDitJC1PApnRtnt5jgsfijdWuaSiU eRQjO6kjpgRtVOQlIz+hSyrPRksjiOY8OP+BGBaOLSFmQKF/Dkq49nk6Tu35mBToYfI8ia6o9ad9jo phgnUAVHAb+HZNPaWujqkDUhtjnj2tEw18prgdSuhZDOg6h8F0asOGLDwphnrAek3sC38g+sqACLjI t4KGvAf/MLwYNA9ikaSgtexLqdviP6zkiRni6rIWS2Yq+reSSGMnhD9dN9hJXQLZn/Fe0bLEO6CK/V 4tNBT8bwGzxQvENSJcZ5J2nEK7E6q0hNscsbSpm26rQk6F5GBzHgYpaanauTxZrAzvdTAKLeI3+ekA 2ldZ2W9gkc3qihSz/5JUWAEhXQnu7vmiEiUiXEJMKNRRl1kR4lAF2nWF5+EeGQOdDNWzuDP3bo2MGY RPn4uZ8FQrQ/wlvt862eva/iKsmIKqTzYp32O+WmGyCqNgisw2umSF8GYzHg== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org 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. Cc: Daniel Vetter Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: David Airlie Cc: dri-devel@lists.freedesktop.org Fixes: 79465e0ffeb9 ("drm/dp: Add helper to get post-cursor adjustments") Signed-off-by: Kees Cook Reviewed-by: Gustavo A. R. Silva Reviewed-by: Jani Nikula Link: https://lore.kernel.org/r/20220105173507.2420910-1-keescook@chromium.org --- drivers/gpu/drm/dp/drm_dp.c | 10 ---------- drivers/gpu/drm/tegra/dp.c | 11 ++++++++++- include/drm/dp/drm_dp_helper.h | 2 -- 3 files changed, 10 insertions(+), 13 deletions(-) diff --git a/drivers/gpu/drm/dp/drm_dp.c b/drivers/gpu/drm/dp/drm_dp.c index e159b81800d4..703972ae14c6 100644 --- a/drivers/gpu/drm/dp/drm_dp.c +++ b/drivers/gpu/drm/dp/drm_dp.c @@ -208,16 +208,6 @@ bool drm_dp_128b132b_link_training_failed(const u8 link_status[DP_LINK_STATUS_SI } EXPORT_SYMBOL(drm_dp_128b132b_link_training_failed); -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 e4369e5b2943..7295975e5733 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/dp/drm_dp_helper.h b/include/drm/dp/drm_dp_helper.h index 2a0e75e69e80..51e02cf75277 100644 --- a/include/drm/dp/drm_dp_helper.h +++ b/include/drm/dp/drm_dp_helper.h @@ -1530,8 +1530,6 @@ 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