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Wed, 26 Oct 2022 05:06:39 -0700 (PDT) Received: from alco.roam.corp.google.com ([2620:0:1059:10:b47a:bedd:2941:1e3f]) by smtp.gmail.com with ESMTPSA id y18-20020a17090668d200b0079e11b8e891sm2892546ejr.125.2022.10.26.05.06.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Oct 2022 05:06:38 -0700 (PDT) From: Ricardo Ribalda Date: Wed, 26 Oct 2022 14:06:11 +0200 Subject: [PATCH v3 6/7] media: uvcvideo: Lock video streams and queues while unregistering MIME-Version: 1.0 Message-Id: <20220920-resend-powersave-v3-6-c47856d8757e@chromium.org> References: <20220920-resend-powersave-v3-0-c47856d8757e@chromium.org> In-Reply-To: <20220920-resend-powersave-v3-0-c47856d8757e@chromium.org> To: Mauro Carvalho Chehab Cc: Tomasz Figa , Ricardo Ribalda , Guenter Roeck , Max Staudt , linux-kernel@vger.kernel.org, Alan Stern , Hans Verkuil , Laurent Pinchart , linux-media@vger.kernel.org X-Mailer: b4 0.11.0-dev-d93f8 X-Developer-Signature: v=1; a=openpgp-sha256; l=4894; i=ribalda@chromium.org; h=from:subject:message-id; bh=HlIWUJ62M0kPqi0HzBoxVqaSaBvxV//ACPhATfL1bx8=; b=owEBbQKS/ZANAwAKAdE30T7POsSIAcsmYgBjWSLE8h3ON1ke3QBn4Z1ZWRgSwdPMJouexkwLx94p AANcweeJAjMEAAEKAB0WIQREDzjr+/4oCDLSsx7RN9E+zzrEiAUCY1kixAAKCRDRN9E+zzrEiAAjD/ wJh1z+QuEXCHql4pl30VsduTLXic9hcSwbyq7NHRhZEGbSy8u4m1BEQnpEfz1b3lxUcVLTAGfKVuQ6 M1Qcy3mOFJI6J42Rm2Ojs7lbEMT9ozmmNqD+5WR9jU7fki5zeY+QvKRNqIituokFvNe+vRIjut7oxB LO9Rm0T1ssFHXxNoKbt1F0/vsZ4J2WjKoNKf80+5P1O6s7aE4DTZDCFWpZMr1aPcp3RqsZI4Wb3l7A /Vo04sTVpaenIzPXHtiWWwI+Q/IepizKN8Cctp4wth1kbqY4z9wAYMqjbNdYssg5ei+hzrnED19rvG aARy73GY6tu+pU6+maVC+KyEezqIAayzTGAANAsYk1Liub0DSnRHi65F0rMUlmvTr7MLYPTqXeUWeO jzHhqB0X8fkzUsvHKjEzj1U8ACtjYRWbG3PRxQ8q7dyMnpsdhbSpsyqKL7Zp2vKeyNz0CRjttRDDch 7/g2hJxp36u4Ozn2ECTUfkODzsgQlO9DGQUxLUMQvu7vW/4wJ2WDm3sNM1QvqOgthyaxWvgZuQY816 9pMfXd8eGV1V4fQBEVneWcSMB0HZiv23pGg51Rgss3W9YGYG4hj8MasT/p3flG7P5ORaS/SFTS6G+G lDF7O+iCmcjZ6idEgKL3yVoLuP02GcfV5NGMabHflmus5jfnFTynjM9Ou28g== X-Developer-Key: i=ribalda@chromium.org; a=openpgp; fpr=9EC3BB66E2FC129A6F90B39556A0D81F9F782DA9 X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747752047750135803?= X-GMAIL-MSGID: =?utf-8?q?1747752047750135803?= From: Guenter Roeck The call to uvc_disconnect() is not protected by any mutex. This means it can and will be called while other accesses to the video device are in progress. This can cause all kinds of race conditions, including crashes such as the following. usb 1-4: USB disconnect, device number 3 BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 0 PID: 5633 Comm: V4L2CaptureThre Not tainted 4.19.113-08536-g5d29ca36db06 #1 Hardware name: GOOGLE Edgar, BIOS Google_Edgar.7287.167.156 03/25/2019 RIP: 0010:usb_ifnum_to_if+0x29/0x40 Code: <...> RSP: 0018:ffffa46f42a47a80 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff904a396c9000 RDX: ffff904a39641320 RSI: 0000000000000001 RDI: 0000000000000000 RBP: ffffa46f42a47a80 R08: 0000000000000002 R09: 0000000000000000 R10: 0000000000009975 R11: 0000000000000009 R12: 0000000000000000 R13: ffff904a396b3800 R14: ffff904a39e88000 R15: 0000000000000000 FS: 00007f396448e700(0000) GS:ffff904a3ba00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000016cb46000 CR4: 00000000001006f0 Call Trace: usb_hcd_alloc_bandwidth+0x1ee/0x30f usb_set_interface+0x1a3/0x2b7 uvc_video_start_transfer+0x29b/0x4b8 [uvcvideo] uvc_video_start_streaming+0x91/0xdd [uvcvideo] uvc_start_streaming+0x28/0x5d [uvcvideo] vb2_start_streaming+0x61/0x143 [videobuf2_common] vb2_core_streamon+0xf7/0x10f [videobuf2_common] uvc_queue_streamon+0x2e/0x41 [uvcvideo] uvc_ioctl_streamon+0x42/0x5c [uvcvideo] __video_do_ioctl+0x33d/0x42a video_usercopy+0x34e/0x5ff ? video_ioctl2+0x16/0x16 v4l2_ioctl+0x46/0x53 do_vfs_ioctl+0x50a/0x76f ksys_ioctl+0x58/0x83 __x64_sys_ioctl+0x1a/0x1e do_syscall_64+0x54/0xde usb_set_interface() should not be called after the USB device has been unregistered. However, in the above case the disconnect happened after v4l2_ioctl() was called, but before the call to usb_ifnum_to_if(). Acquire various mutexes in uvc_unregister_video() to fix the majority (maybe all) of the observed race conditions. The uvc_device lock prevents races against suspend and resume calls and the poll function. The uvc_streaming lock prevents races against stream related functions; for the most part, those are ioctls. This lock also requires other functions using this lock to check if a video device is still registered after acquiring it. For example, it was observed that the video device was already unregistered by the time the stream lock was acquired in uvc_ioctl_streamon(). The uvc_queue lock prevents races against queue functions, Most of those are already protected by the uvc_streaming lock, but some are called directly. This is done as added protection; an actual race was not (yet) observed. Cc: Laurent Pinchart Cc: Alan Stern Cc: Hans Verkuil Signed-off-by: Guenter Roeck diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c index dc43100d0f95..b67d753d27ae 100644 --- a/drivers/media/usb/uvc/uvc_driver.c +++ b/drivers/media/usb/uvc/uvc_driver.c @@ -1889,16 +1889,24 @@ static void uvc_unregister_video(struct uvc_device *dev) { struct uvc_streaming *stream; + mutex_lock(&dev->lock); + list_for_each_entry(stream, &dev->streams, list) { if (!video_is_registered(&stream->vdev)) continue; + mutex_lock(&stream->mutex); + mutex_lock(&stream->queue.mutex); + video_unregister_device(&stream->vdev); video_unregister_device(&stream->meta.vdev); uvc_debugfs_cleanup_stream(stream); vb2_queue_release(&stream->queue.queue); + + mutex_unlock(&stream->queue.mutex); + mutex_unlock(&stream->mutex); } if (dev->int_ep) @@ -1911,6 +1919,8 @@ static void uvc_unregister_video(struct uvc_device *dev) if (media_devnode_is_registered(dev->mdev.devnode)) media_device_unregister(&dev->mdev); #endif + + mutex_unlock(&dev->lock); } int uvc_register_video_device(struct uvc_device *dev, diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c index 77b687c46082..b4f2da336def 100644 --- a/drivers/media/usb/uvc/uvc_v4l2.c +++ b/drivers/media/usb/uvc/uvc_v4l2.c @@ -37,14 +37,20 @@ static int uvc_pm_get(struct uvc_streaming *stream) if (ret) return ret; + mutex_lock(&stream->dev->lock); + + if (!video_is_registered(&stream->vdev)) + goto done; + if (!stream->dev->int_ep) - return 0; + goto done; - mutex_lock(&stream->dev->lock); if (!stream->dev->users) ret = uvc_status_start(stream->dev, GFP_KERNEL); if (!ret) stream->dev->users++; + +done: mutex_unlock(&stream->dev->lock); if (ret)