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([2a01:e0a:c:37e0:8998:e0cf:68cc:1b62]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47d7f653cd6sm67348115e9.9.2026.01.06.13.33.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 06 Jan 2026 13:33:00 -0800 (PST) Message-ID: <76fb4c29-2c7b-4971-92d6-365b5782aec6@redhat.com> Date: Tue, 6 Jan 2026 22:32:58 +0100 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 1/2] drm/panic: Ensure drm_panic_type is initialized to a valid value To: Nathan Chancellor , Javier Martinez Canillas , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Tvrtko Ursulin Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20260105-drm_panic-handle-invalid-drm_panic_screen-v1-0-55228bd4b0f8@kernel.org> <20260105-drm_panic-handle-invalid-drm_panic_screen-v1-1-55228bd4b0f8@kernel.org> Content-Language: en-US, fr From: Jocelyn Falempe In-Reply-To: <20260105-drm_panic-handle-invalid-drm_panic_screen-v1-1-55228bd4b0f8@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 06/01/2026 07:19, Nathan Chancellor wrote: > If a user has set an invalid CONFIG_DRM_PANIC_SCREEN value (such as > "qr_code" without CONFIG_DRM_PANIC_SCREEN_QR_CODE=y due to missing or > incorrect Rust dependencies), there is a panic when accessing > /sys/module/drm/parameters/panic_screen: > > [ 12.218375] BUG: unable to handle page fault for address: 0000000796dd8818 > [ 12.219737] #PF: supervisor read access in kernel mode > ... > [ 12.227167] RIP: 0010:drm_panic_type_get+0x1b/0x30 > > If drm_panic_type_set() does not find a valid drm_panic_type enumeration > in drm_panic_type_map based on the provided value, it does not change > drm_panic_type from the default -1 value, which is not a valid index for > accessing drm_panic_type_map in drm_panic_type_get(), resulting in the > crash. > > Validate the value of CONFIG_DRM_PANIC_SCREEN at boot time via the > return value of drm_panic_type_set() in drm_panic_init() and explicitly > fall back to the default of "user" with a message to the user so that > they can adjust their configuration or fix missing dependencies. > > [ 0.800697] Unsupported value for CONFIG_DRM_PANIC_SCREEN ('qr_code'), falling back to 'user'... > Good catch, thanks for the fix. Reviewed-by: Jocelyn Falempe > Fixes: e85e9ccf3f84 ("drm/panic: Report invalid or unsupported panic modes") > Signed-off-by: Nathan Chancellor > --- > drivers/gpu/drm/drm_panic.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c > index eb7ef17b9c71..0cd574dd9d88 100644 > --- a/drivers/gpu/drm/drm_panic.c > +++ b/drivers/gpu/drm/drm_panic.c > @@ -1072,8 +1072,11 @@ void drm_panic_unregister(struct drm_device *dev) > */ > void __init drm_panic_init(void) > { > - if (drm_panic_type == -1) > - drm_panic_type_set(CONFIG_DRM_PANIC_SCREEN, NULL); > + if (drm_panic_type == -1 && drm_panic_type_set(CONFIG_DRM_PANIC_SCREEN, NULL)) { > + pr_warn("Unsupported value for CONFIG_DRM_PANIC_SCREEN ('%s'), falling back to 'user'...\n", > + CONFIG_DRM_PANIC_SCREEN); > + drm_panic_type = DRM_PANIC_TYPE_USER; > + } > drm_panic_qr_init(); > } > >