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([2405:201:682f:383f:9626:1a7c:c4cf:3e3b]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36a428ecb61sm33556442eec.10.2026.11.02.06.15.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Nov 2026 06:15:18 -0800 (PST) From: Deepanshu Kartikey To: mchehab@kernel.org, sakari.ailus@linux.intel.com, laurent.pinchart@ideasonboard.com, hverkuil@kernel.org Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Deepanshu Kartikey , stable@vger.kernel.org Subject: [PATCH 2/2] media: mc: fix race in media_device_unregister_entity() Date: Mon, 2 Nov 2026 19:44:39 +0530 Message-ID: <20261102141439.13505-3-kartikey406@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261102141439.13505-1-kartikey406@gmail.com> References: <20261102141439.13505-1-kartikey406@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit media_device_unregister_entity() checks entity->graph_obj.mdev for NULL before taking mdev->graph_mutex, but does not check again afterwards. If media_device_unregister() runs concurrently (for example on USB disconnect), it unregisters every entity and clears graph_obj.mdev while this function waits for the mutex. The waiter then calls __media_device_unregister_entity() with a NULL mdev and faults in ida_free(&mdev->entity_internal_idx, ...): Oops: general protection fault, KASAN: null-ptr-deref in range [0x00000000000000c8-0x00000000000000cf] ida_free __media_device_unregister_entity media_device_unregister_entity v4l2_device_release v4l2_open Re-check graph_obj.mdev under the lock and skip the unregister if the entity is already gone. Found while testing the fix for the syzbot report at https://syzkaller.appspot.com/bug?extid=54648a6c1187a7ef46a6 Fixes: e2c91d4d78ee ("[media] media-device: get rid of the spinlock") Cc: stable@vger.kernel.org Signed-off-by: Deepanshu Kartikey --- drivers/media/mc/mc-device.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/media/mc/mc-device.c b/drivers/media/mc/mc-device.c index f8ea7cfe10b2..039ef7d04ac7 100644 --- a/drivers/media/mc/mc-device.c +++ b/drivers/media/mc/mc-device.c @@ -674,7 +674,8 @@ void media_device_unregister_entity(struct media_entity *entity) return; mutex_lock(&mdev->graph_mutex); - __media_device_unregister_entity(entity); + if (entity->graph_obj.mdev) + __media_device_unregister_entity(entity); mutex_unlock(&mdev->graph_mutex); } EXPORT_SYMBOL_GPL(media_device_unregister_entity); -- 2.43.0