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Mon, 02 Jan 2023 06:48:09 -0800 (PST) Received: from alco.roam.corp.google.com ([2620:0:1059:10:6ef6:ea10:76ec:977f]) by smtp.gmail.com with ESMTPSA id k3-20020a17090632c300b00781dbdb292asm13064795ejk.155.2023.01.02.06.48.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Jan 2023 06:48:09 -0800 (PST) From: Ricardo Ribalda Date: Mon, 02 Jan 2023 15:48:01 +0100 Subject: [PATCH v6] media: uvcvideo: Fix race condition with usb_kill_urb MIME-Version: 1.0 Message-Id: <20221212-uvc-race-v6-0-2a662f8de011@chromium.org> To: Laurent Pinchart , Mauro Carvalho Chehab , Max Staudt , Sergey Senozhatsky Cc: Yunke Cao , linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, stable@vger.kernel.org, Ricardo Ribalda X-Mailer: b4 0.11.0-dev-696ae X-Developer-Signature: v=1; a=openpgp-sha256; l=5952; i=ribalda@chromium.org; h=from:subject:message-id; bh=OlBUT0d0UDR2+oDUQbmPwKuQ+fnKJ1FL06u1EsfTbt8=; b=owEBbQKS/ZANAwAKAdE30T7POsSIAcsmYgBjsu6ick7OJ1WRu4rYZaD1P3Xj9qmSGYqV/7icskpq t+TImPKJAjMEAAEKAB0WIQREDzjr+/4oCDLSsx7RN9E+zzrEiAUCY7LuogAKCRDRN9E+zzrEiEMiD/ 93msrnCV2Ux9hqvFn3RKES7xI+hZLJCiuw1Y9XBxrP4p6CzOjicG8ZEL5rLwB6lPfh3Ipe+T2bWESv OHdn12VvQ3ydnaibggh1ZBJh9FyHRyrQFoWOyy0TufwQE8d5nmwLgCHOew0dnTBa+zszwAwZcWjYOK tFgrw8J8mqRalRUV4JZQDdLSvjn/MVjv5hZ00iWQK8pXhrmgMkrkgScrNkBC9tngDLC9JZBeFkuyzd dB/ZSo0ItexKTspXMvJ25TPAkCplKvCCjc1LzMQBJYpNKKBQQ4R76+sXhjaf+D7JvqGVBsBkBV8Q9Y KnxKp31V8twHhhbQQOvcJiLWXp24gZOsP1CK9X8xBFTfEh1Zx4nUcIKE3eeP0ohA87d3nnVjvfc2X6 ncJWKHZ3yq1MN2fHDIzN4L5b2EcQmMJsoO2gy3Ach/d/ItODlt0rI8up5rWuG4N2lwyBUWAib4uQZq eVfc96dpe0hbv2qlPS2WIw6OaERLeP831Z01NwId8S/Wj5fP7p7HgVjam1HswZutlv0q7vjTm5y7ri 4fceDwrlplf3gexCa7KXeie4Xqs2w95uGf+TBU91bUglNXq2MdrSbnNYyjtb7TwcU67O8vxVW0OM2Q EN0no2ac3JcmqZpwUbTE9kmLk0aNXeB5I9MAks4Z80rSShxE1AgN2bJcKhXw== 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?1752208104024059594?= X-GMAIL-MSGID: =?utf-8?q?1753923286325496056?= 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 --- uvc: Fix race condition on uvc Make sure that all the async work is finished when we stop the status urb. 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 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 | 3 +++ drivers/media/usb/uvc/uvc_status.c | 40 ++++++++++++++++++++++++++++++++++++++ drivers/media/usb/uvc/uvcvideo.h | 1 + 3 files changed, 44 insertions(+) --- base-commit: 0ec5a38bf8499f403f81cb81a0e3a60887d1993c 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 c95a2229f4fa..5160facc8e20 100644 --- a/drivers/media/usb/uvc/uvc_ctrl.c +++ b/drivers/media/usb/uvc/uvc_ctrl.c @@ -1442,6 +1442,9 @@ static void uvc_ctrl_status_event_work(struct work_struct *work) uvc_ctrl_status_event(w->chain, w->ctrl, w->data); + if (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 7518ffce22ed..e457889345a3 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 @@ -309,5 +310,44 @@ 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 */ + dev->flush_status = true; + + /* + * 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_mb(); + + /* 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. + */ + dev->flush_status = false; + + /* + * Write to memory the value of flush_status before uvc_status_start() + * is called again. + */ + smp_mb(); } diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h index df93db259312..6a9b72d6789e 100644 --- a/drivers/media/usb/uvc/uvcvideo.h +++ b/drivers/media/usb/uvc/uvcvideo.h @@ -560,6 +560,7 @@ struct uvc_device { struct usb_host_endpoint *int_ep; struct urb *int_urb; u8 *status; + bool flush_status; struct input_dev *input; char input_phys[64];