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[199.106.103.254]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-326798cb9f5sm10948965eec.13.2026.08.17.14.21.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 17 Aug 2026 14:21:12 -0700 (PDT) Message-ID: Date: Mon, 17 Aug 2026 15:21:11 -0600 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: check for NULL master in drm_getunique() and drm_getmagic() To: moonafterrain@outlook.com, Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Melissa Wen , Dave Airlie , Jacek Lawrynowicz , Oded Gabbay Cc: Greg Kroah-Hartman , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Yuhao Jiang , stable@vger.kernel.org References: <20260815-drm-accel-null-master-v1-1-93bdd3ba52f1@outlook.com> Content-Language: en-US From: Jeff Hugo In-Reply-To: <20260815-drm-accel-null-master-v1-1-93bdd3ba52f1@outlook.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: 5emVH7TJHSkGZafzCaCUBvssqnwwTzu_ X-Proofpoint-Spam-Info: AW1haW4tMjYwODE3MDE2MiBTYWx0ZWRfX0SAx8Tv9SX2Y xFygXdpYMrHnsPqIRazegFqxzZeVN73lY/uUWthgnmvy5kxIhXcBntXkmXuUdugEg/v6woGPFCN zTWWSRpnowywY8BsRSoTAREdo6ogxfU= X-Authority-Analysis: v=2.4 cv=SuCgLvO0 c=1 sm=1 tr=0 ts=6a837b4b cx=c_pps a=IZJwPbhc+fLeJZngyXXI0A==:117 a=JYp8KDb2vCoCEuGobkYCKw==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yx91gb_oNiZeI1HMLzn7:22 a=UqCG9HQmAAAA:8 a=pGLkceISAAAA:8 a=VwQbUJbxAAAA:8 a=EUspDBNiAAAA:8 a=djIpYLbIsOyqsb7DCLUA:9 a=QEXdDO2ut3YA:10 a=uG9DUKGECoFWVXl0Dc02:22 X-Proofpoint-ORIG-GUID: 5emVH7TJHSkGZafzCaCUBvssqnwwTzu_ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODE3MDE2MiBTYWx0ZWRfX//qsVRr3gFTE eae7I3Qg6IZdQG1xrKGJIaft+OZ+zA8DQIW6tgNOh/KcoWtck5SzZAw6vbvZweYN73iqt7wywX1 IK+hF+9kOXQLe2m9bNVnmylAIFmRZ4wtRO6r1Kv0ZfAaCzfiiBhJIf1poTGVwmK41/xFyKpxWla r+UH0MKAiPSM4RZsSyIpDzZYh/JHbl3/mR9wRCemQtj1lS9bGtwJONS7gX5i/iuuypxfd0VP9FM +vCkVo9LqleJY/FNiE5yEoZeICjngVFmdp1vJDHw4fqSd+uL3HfnjQi0v98qZ0OtJX8KJVgIBpq BS5wDih/G67r0ej9VfzbrbloYxg+2x92s87F1UR/NEssGa4EOwbCdx0hAuzBDN+ZCs9o8AQ9QrI nzJy5nN7smOP8FIb4itobMx98ntyyVggf/DmRuXrgaKFfgpEJuRash51IYFu6PjGL/0x3SSzccQ hzDgvhVjZ20hAP9WwWA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-17_03,2026-08-12_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 priorityscore=1501 phishscore=0 clxscore=1015 impostorscore=0 lowpriorityscore=0 suspectscore=0 adultscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608170162 On 8/15/2026 12:37 AM, Junrui Luo via B4 Relay wrote: > From: Junrui Luo > > drm_getunique() and drm_getmagic() dereference file_priv->master without > checking it, and both ioctls are registered with flags of 0. > drm_open_helper() only calls drm_master_open() for primary clients, so a > drm_file opened on a non-primary minor keeps master == NULL. Render > clients are already rejected by the DRM_RENDER_ALLOW test in > drm_ioctl_permit(), so before commit 2c204f3d5321 ("accel: add dedicated > minor for accelerator devices") every drm_file reaching these ioctls had > a master. > > DRM_MINOR_ACCEL is neither primary nor render: it gets no master in > drm_open_helper() and is not covered by drm_is_render_client(). Issuing > DRM_IOCTL_GET_UNIQUE or DRM_IOCTL_GET_MAGIC on /dev/accel/accel* leads > to a NULL pointer dereference, in drm_getunique() with dev->master_mutex > held. The compat entry point reaches drm_getunique() through > drm_ioctl_kernel() with flags of 0 as well. > > Return -EINVAL when master is NULL, matching drm_setmaster_ioctl(). > > Fixes: 2c204f3d5321 ("accel: add dedicated minor for accelerator devices") > Reported-by: Yuhao Jiang > Assisted-by: Claude:claude-opus-5 > Cc: stable@vger.kernel.org > Signed-off-by: Junrui Luo Reviewed-by: Jeff Hugo