From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762710AbdAJOyt (ORCPT ); Tue, 10 Jan 2017 09:54:49 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:60570 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1765685AbdAJNoh (ORCPT ); Tue, 10 Jan 2017 08:44:37 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ioan-Adrian Ratiu , Takashi Iwai Subject: [PATCH 4.9 007/206] ALSA: usb-audio: Fix irq/process data synchronization Date: Tue, 10 Jan 2017 14:34:50 +0100 Message-Id: <20170110131503.100493238@linuxfoundation.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170110131502.767555407@linuxfoundation.org> References: <20170110131502.767555407@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ioan-Adrian Ratiu commit 1d0f953086f090a022f2c0e1448300c15372db46 upstream. Commit 16200948d83 ("ALSA: usb-audio: Fix race at stopping the stream") was incomplete causing another more severe kernel panic, so it got reverted. This fixes both the original problem and its fallout kernel race/crash. The original fix is to move the endpoint member NULL clearing logic inside wait_clear_urbs() so the irq triggering the urb completion doesn't call retire_capture/playback_urb() after the NULL clearing and generate a panic. However this creates a new race between snd_usb_endpoint_start()'s call to wait_clear_urbs() and the irq urb completion handler which again calls retire_capture/playback_urb() leading to a new NULL dereference. We keep the EP deactivation code in snd_usb_endpoint_start() because removing it will break the EP reference counting (see [1] [2] for info), however we don't need the "can_sleep" mechanism anymore because a new function was introduced (snd_usb_endpoint_sync_pending_stop()) which synchronizes pending stops and gets called inside the pcm prepare callback. It also makes sense to remove can_sleep because it was also removed from deactivate_urbs() signature in [3] so we benefit from more simplification. [1] commit 015618b90 ("ALSA: snd-usb: Fix URB cancellation at stream start") [2] commit e9ba389c5 ("ALSA: usb-audio: Fix scheduling-while-atomic bug in PCM capture stream") [3] commit ccc1696d5 ("ALSA: usb-audio: simplify endpoint deactivation code") Fixes: f8114f8583bb ("Revert "ALSA: usb-audio: Fix race at stopping the stream"") Signed-off-by: Ioan-Adrian Ratiu Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/usb/endpoint.c | 17 +++++++---------- sound/usb/endpoint.h | 2 +- sound/usb/pcm.c | 10 +++++----- 3 files changed, 13 insertions(+), 16 deletions(-) --- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -534,6 +534,11 @@ static int wait_clear_urbs(struct snd_us alive, ep->ep_num); clear_bit(EP_FLAG_STOPPING, &ep->flags); + ep->data_subs = NULL; + ep->sync_slave = NULL; + ep->retire_data_urb = NULL; + ep->prepare_data_urb = NULL; + return 0; } @@ -898,9 +903,7 @@ int snd_usb_endpoint_set_params(struct s /** * snd_usb_endpoint_start: start an snd_usb_endpoint * - * @ep: the endpoint to start - * @can_sleep: flag indicating whether the operation is executed in - * non-atomic context + * @ep: the endpoint to start * * A call to this function will increment the use count of the endpoint. * In case it is not already running, the URBs for this endpoint will be @@ -910,7 +913,7 @@ int snd_usb_endpoint_set_params(struct s * * Returns an error if the URB submission failed, 0 in all other cases. */ -int snd_usb_endpoint_start(struct snd_usb_endpoint *ep, bool can_sleep) +int snd_usb_endpoint_start(struct snd_usb_endpoint *ep) { int err; unsigned int i; @@ -924,8 +927,6 @@ int snd_usb_endpoint_start(struct snd_us /* just to be sure */ deactivate_urbs(ep, false); - if (can_sleep) - wait_clear_urbs(ep); ep->active_mask = 0; ep->unlink_mask = 0; @@ -1006,10 +1007,6 @@ void snd_usb_endpoint_stop(struct snd_us if (--ep->use_count == 0) { deactivate_urbs(ep, false); - ep->data_subs = NULL; - ep->sync_slave = NULL; - ep->retire_data_urb = NULL; - ep->prepare_data_urb = NULL; set_bit(EP_FLAG_STOPPING, &ep->flags); } } --- a/sound/usb/endpoint.h +++ b/sound/usb/endpoint.h @@ -18,7 +18,7 @@ int snd_usb_endpoint_set_params(struct s struct audioformat *fmt, struct snd_usb_endpoint *sync_ep); -int snd_usb_endpoint_start(struct snd_usb_endpoint *ep, bool can_sleep); +int snd_usb_endpoint_start(struct snd_usb_endpoint *ep); void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep); void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep); int snd_usb_endpoint_activate(struct snd_usb_endpoint *ep); --- a/sound/usb/pcm.c +++ b/sound/usb/pcm.c @@ -218,7 +218,7 @@ int snd_usb_init_pitch(struct snd_usb_au } } -static int start_endpoints(struct snd_usb_substream *subs, bool can_sleep) +static int start_endpoints(struct snd_usb_substream *subs) { int err; @@ -231,7 +231,7 @@ static int start_endpoints(struct snd_us dev_dbg(&subs->dev->dev, "Starting data EP @%p\n", ep); ep->data_subs = subs; - err = snd_usb_endpoint_start(ep, can_sleep); + err = snd_usb_endpoint_start(ep); if (err < 0) { clear_bit(SUBSTREAM_FLAG_DATA_EP_STARTED, &subs->flags); return err; @@ -260,7 +260,7 @@ static int start_endpoints(struct snd_us dev_dbg(&subs->dev->dev, "Starting sync EP @%p\n", ep); ep->sync_slave = subs->data_endpoint; - err = snd_usb_endpoint_start(ep, can_sleep); + err = snd_usb_endpoint_start(ep); if (err < 0) { clear_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags); return err; @@ -839,7 +839,7 @@ static int snd_usb_pcm_prepare(struct sn /* for playback, submit the URBs now; otherwise, the first hwptr_done * updates for all URBs would happen at the same time when starting */ if (subs->direction == SNDRV_PCM_STREAM_PLAYBACK) - ret = start_endpoints(subs, true); + ret = start_endpoints(subs); unlock: snd_usb_unlock_shutdown(subs->stream->chip); @@ -1655,7 +1655,7 @@ static int snd_usb_substream_capture_tri switch (cmd) { case SNDRV_PCM_TRIGGER_START: - err = start_endpoints(subs, false); + err = start_endpoints(subs); if (err < 0) return err;