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Wed, 8 Jan 2025 23:37:31 +0100 (CET) Message-ID: Date: Thu, 9 Jan 2025 00:37:31 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/connector: hdmi: Handle NULL display mode in state check helper To: Maxime Ripard Cc: Maarten Lankhorst , Thomas Zimmermann , David Airlie , Simona Vetter , Dave Stevenson , Dmitry Baryshkov , kernel@collabora.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20250107-hdmi-conn-null-mode-v1-1-fff4be46d106@collabora.com> <20250107-dangerous-shapeless-bandicoot-dc74dd@houat> Content-Language: en-US From: Cristian Ciocaltea In-Reply-To: <20250107-dangerous-shapeless-bandicoot-dc74dd@houat> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/7/25 5:16 PM, Maxime Ripard wrote: > On Tue, Jan 07, 2025 at 02:00:35AM +0200, Cristian Ciocaltea wrote: >> drm_atomic_helper_connector_hdmi_check() helper makes use of >> connector_state_get_mode() to obtain a drm_display_mode pointer, but it >> doesn't validate it, which may lead to a NULL pointer dereference in >> some cases, i.e. unloading a DRM module: >> >> [ 1002.910414] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 >> [...] >> [ 1002.923833] Hardware name: Radxa ROCK 5B (DT) >> [ 1002.924819] pc : drm_match_cea_mode+0x30/0x280 [drm] >> [ 1002.925318] lr : hdmi_try_format_bpc+0x7c/0x580 [drm_display_helper] >> [...] >> [ 1002.932411] Call trace: >> [ 1002.932626] drm_match_cea_mode+0x30/0x280 [drm] (P) >> [ 1002.933120] hdmi_try_format_bpc+0x7c/0x580 [drm_display_helper] >> [ 1002.933662] drm_atomic_helper_connector_hdmi_check+0x10c/0x478 [drm_display_helper] >> [ 1002.934355] drm_bridge_connector_atomic_check+0x20/0x40 [drm_display_helper] >> [ 1002.934993] drm_atomic_helper_check_modeset+0x698/0xd28 [drm_kms_helper] >> [ 1002.935607] drm_atomic_helper_check+0x28/0xb8 [drm_kms_helper] >> [ 1002.936143] drm_atomic_check_only+0x794/0x988 [drm] >> [ 1002.936635] drm_atomic_commit+0x60/0xe0 [drm] >> [ 1002.937082] drm_atomic_helper_disable_all+0x184/0x218 [drm_kms_helper] >> [ 1002.937678] drm_atomic_helper_shutdown+0x90/0x150 [drm_kms_helper] >> [ 1002.938243] rockchip_drm_unbind+0x38/0x80 [rockchipdrm] >> [ 1002.938720] component_master_del+0xac/0xf8 >> [ 1002.939089] rockchip_drm_platform_remove+0x34/0x78 [rockchipdrm] >> [...] >> >> Add the missing NULL check before passing the mode pointer further. >> >> Fixes: f035f4097f1e ("drm/connector: hdmi: Calculate TMDS character rate") >> Signed-off-by: Cristian Ciocaltea > > Looks good to me, but we need to provide a test for that case too Test cases provided in v2: https://lore.kernel.org/lkml/20250109-hdmi-conn-null-mode-v2-2-9eeaf1109547@collabora.com/ Thanks, Cristian