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Thu, 05 Jan 2023 06:31:45 -0800 (PST) Received: from alco.roam.corp.google.com ([2620:0:1059:10:848f:5924:dffa:3b5c]) by smtp.gmail.com with ESMTPSA id c4-20020aa7c984000000b004873927780bsm10818084edt.20.2023.01.05.06.31.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Jan 2023 06:31:44 -0800 (PST) From: Ricardo Ribalda Date: Thu, 05 Jan 2023 15:31:29 +0100 Subject: [PATCH v7] media: uvcvideo: Fix race condition with usb_kill_urb MIME-Version: 1.0 Message-Id: <20221212-uvc-race-v7-0-e2517c66a55a@chromium.org> To: Sergey Senozhatsky , Hillf Danton , Mauro Carvalho Chehab , Laurent Pinchart , Max Staudt Cc: Ricardo Ribalda , Yunke Cao , linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, stable@vger.kernel.org X-Mailer: b4 0.11.0-dev-696ae X-Developer-Signature: v=1; a=openpgp-sha256; l=6479; i=ribalda@chromium.org; h=from:subject:message-id; bh=cW2kwv2siZICftxj75pqCs1K4XmG0NtU3yyQXAzdBG4=; b=owEBbQKS/ZANAwAKAdE30T7POsSIAcsmYgBjtt9JhJKajr03HfmLDxie/eqxiOch8paSA4cqVoct S4TdcW+JAjMEAAEKAB0WIQREDzjr+/4oCDLSsx7RN9E+zzrEiAUCY7bfSQAKCRDRN9E+zzrEiFyeD/ 92GkSmfrDtKn8ZTQGY6JNCoQA7Yh7pbAvIn/+G0H0e2+A8d9Fcc4BrYob+WxcFsfrhapFdJgZx2Pbn 3Tu8XCG2B6Pm5yWP4Lok3Dh+DrHEdS3+/Hrwwo8zkP9ZCsHF+klVHVZp+yKi9LLUEDW6yUAoPpCf+M p9CNSIIV9Xf+T76bwb8k9h5E8aoy+IYvQWl6yCIboANF1Cg7pcycXerkP5qiLz5Jb9BSmtbEXeqlIC nqXRPuUMDV4Er6lnzNPbyIttEHqqyrr+ml3UvWIpfmCIxRM9eI7B/gzudWW4LoqOeZ4qp7cXYPpGua GjkZBXWSu5OF6RO1aUdvVJsOupJLFmWXBVZp2dvfx4V1ye1v5QFQMD8anl3cyeWgVtMWrgG4WZqYtq LLbluvTvdMW5ZqSWiwWdk6iE5YYHgOWVT7SbxSzJLOHeRb9qi3HuZETQyluzjYRAHDA0vWrvvzxA6N xOHW2pFwBkTphznOd7+y2Id9SIwzdgwsgGnCkCSPUGJ2M90OpnpjPwITti6Ywm5g6gwSHZ2+L9aQtW M15xeaKDfzClDp2y0L8tE9/raf3H2NC9M8e510cVVwAHj2IY97JM9n6Ri40ZYO+UdImbqiFjHhHqAO qdViYbLxaESv4umeSyYe5u9zsbzedumqjw9uyCzJRcl0P7paYBULLvnBxuNw== X-Developer-Key: i=ribalda@chromium.org; a=openpgp; fpr=9EC3BB66E2FC129A6F90B39556A0D81F9F782DA9 X-Spam-Status: No, score=-2.1 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 autolearn=unavailable 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?1754194397951672163?= X-GMAIL-MSGID: =?utf-8?q?1754194397951672163?= usb_kill_urb warranties that all the handlers are finished when it returns, but does not protect against threads that might be handling asynchronously the urb. For UVC, the function uvc_ctrl_status_event_async() takes care of control changes asynchronously. If the code is executed in the following order: CPU 0 CPU 1 ===== ===== uvc_status_complete() uvc_status_stop() uvc_ctrl_status_event_work() uvc_status_start() -> FAIL Then uvc_status_start will keep failing and this error will be shown: <4>[ 5.540139] URB 0000000000000000 submitted while active drivers/usb/core/urb.c:378 usb_submit_urb+0x4c3/0x528 Let's improve the current situation, by not re-submiting the urb if we are stopping the status event. Also process the queued work (if any) during stop. CPU 0 CPU 1 ===== ===== uvc_status_complete() uvc_status_stop() uvc_status_start() uvc_ctrl_status_event_work() -> FAIL Hopefully, with the usb layer protection this should be enough to cover all the cases. Cc: stable@vger.kernel.org Fixes: e5225c820c05 ("media: uvcvideo: Send a control event when a Control Change interrupt arrives") Reviewed-by: Yunke Cao Signed-off-by: Ricardo Ribalda Reviewed-by: Laurent Pinchart --- uvc: Fix race condition on uvc Make sure that all the async work is finished when we stop the status urb. To: Hillf Danton To: Yunke Cao To: Sergey Senozhatsky To: Max Staudt To: Laurent Pinchart To: Mauro Carvalho Chehab Cc: linux-media@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- Changes in v7: - Use smp_store_release. (Thanks Hilf!) - Rebase on top of uvc/next. - Link to v6: https://lore.kernel.org/r/20221212-uvc-race-v6-0-2a662f8de011@chromium.org Changes in v6: - Improve comments. (Thanks Laurent). - Use true/false instead of 1/0 (Thanks Laurent). - Link to v5: https://lore.kernel.org/r/20221212-uvc-race-v5-0-3db3933d1608@chromium.org Changes in v5: - atomic_t do not impose barriers, use smp_mb() instead. (Thanks Laurent) - Add an extra cancel_work_sync(). - Link to v4: https://lore.kernel.org/r/20221212-uvc-race-v4-0-38d7075b03f5@chromium.org Changes in v4: - Replace bool with atomic_t to avoid compiler reordering. - First complete the async work and then kill the urb to avoid race (Thanks Laurent!) - Link to v3: https://lore.kernel.org/r/20221212-uvc-race-v3-0-954efc752c9a@chromium.org Changes in v3: - Remove the patch for dev->status, makes more sense in another series, and makes the zero day less nervous. - Update reviewed-by (thanks Yunke!). - Link to v2: https://lore.kernel.org/r/20221212-uvc-race-v2-0-54496cc3b8ab@chromium.org Changes in v2: - Add a patch for not kalloc dev->status - Redo the logic mechanism, so it also works with suspend (Thanks Yunke!) - Link to v1: https://lore.kernel.org/r/20221212-uvc-race-v1-0-c52e1783c31d@chromium.org --- drivers/media/usb/uvc/uvc_ctrl.c | 5 +++++ drivers/media/usb/uvc/uvc_status.c | 33 +++++++++++++++++++++++++++++++++ drivers/media/usb/uvc/uvcvideo.h | 1 + 3 files changed, 39 insertions(+) --- base-commit: fb1316b0ff3fc3cd98637040ee17ab7be753aac7 change-id: 20221212-uvc-race-09276ea68bf8 Best regards, diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c index e07b56bbf853..30c417768376 100644 --- a/drivers/media/usb/uvc/uvc_ctrl.c +++ b/drivers/media/usb/uvc/uvc_ctrl.c @@ -6,6 +6,7 @@ * Laurent Pinchart (laurent.pinchart@ideasonboard.com) */ +#include #include #include #include @@ -1509,6 +1510,10 @@ static void uvc_ctrl_status_event_work(struct work_struct *work) uvc_ctrl_status_event(w->chain, w->ctrl, w->data); + /* The barrier is needed to synchronize with uvc_status_stop(). */ + if (smp_load_acquire(&dev->flush_status)) + return; + /* Resubmit the URB. */ w->urb->interval = dev->int_ep->desc.bInterval; ret = usb_submit_urb(w->urb, GFP_KERNEL); diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c index 602830a8023e..21e13b8441da 100644 --- a/drivers/media/usb/uvc/uvc_status.c +++ b/drivers/media/usb/uvc/uvc_status.c @@ -6,6 +6,7 @@ * Laurent Pinchart (laurent.pinchart@ideasonboard.com) */ +#include #include #include #include @@ -311,5 +312,37 @@ int uvc_status_start(struct uvc_device *dev, gfp_t flags) void uvc_status_stop(struct uvc_device *dev) { + struct uvc_ctrl_work *w = &dev->async_ctrl; + + /* + * Prevent the asynchronous control handler from requeing the URB. The + * barrier is needed so the flush_status change is visible to other + * CPUs running the asynchronous handler before usb_kill_urb() is + * called below. + */ + smp_store_release(&dev->flush_status, true); + + /* If there is any status event on the queue, process it. */ + if (cancel_work_sync(&w->work)) + uvc_ctrl_status_event(w->chain, w->ctrl, w->data); + + /* Kill the urb. */ usb_kill_urb(dev->int_urb); + + /* + * The URB completion handler may have queued asynchronous work. This + * won't resubmit the URB as flush_status is set, but it needs to be + * cancelled before returning or it could then race with a future + * uvc_status_start() call. + */ + if (cancel_work_sync(&w->work)) + uvc_ctrl_status_event(w->chain, w->ctrl, w->data); + + /* + * From this point, there are no events on the queue and the status URB + * is dead, this is, no events will be queued until uvc_status_start() + * is called. The barrier is needed to make sure that it is written to + * memory before uvc_status_start() is called again. + */ + smp_store_release(&dev->flush_status, false); } diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h index ae0066eceffd..b2b277cccbdb 100644 --- a/drivers/media/usb/uvc/uvcvideo.h +++ b/drivers/media/usb/uvc/uvcvideo.h @@ -578,6 +578,7 @@ struct uvc_device { struct usb_host_endpoint *int_ep; struct urb *int_urb; struct uvc_status *status; + bool flush_status; struct input_dev *input; char input_phys[64];