From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELvsZjAHWxZtTSoaU048orC25btsFh2e9MBfhxYMht06tiEfxsiQCdzU8egS9KhpXln84aPA ARC-Seal: i=1; a=rsa-sha256; t=1522168254; cv=none; d=google.com; s=arc-20160816; b=Xb5uibmxc8vdhOFC4zr0iytG3CYIF4n+Brhm9037LTlQRipsNCetQ1usRkMI3iDzY3 O8XbLGj4LMNNSPdVH2qIdV9S1CP4d8MyEF/zvQd/ZY+jN92aXZr7e6itgXk2LwQWZhRo Oe3lABxutq9rtJfBrW4gDe27k7fYQ4CG8gel6jgzrHKUYM9L57Q0uNOxCa2UNuU0DuvC nu2LIsUEAwYtmLjepLlkEyJRbSojMOm/suiWITRRbUxTMbHGaiZhtTz4Bl+j3Uh/5pWc zSAxzcJUZ3m/5s/XlkYQfIqptNjlszv0dI4Zf6nlOCIk0VNz0ZJxIPz5Qhx9UzQiEZgq YtIg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=9c0u8kfxUm/1XOMHBcU8Zj/zyNOuEELO7WNuKq8Mopw=; b=hF1DkSkY37GIZbWYr+Eb4VLuR3UfErGQFr//LzXAFFtjqIIVlVgGJPWJM914gfcopx b8aWennx/pViJHOtDFVYvzXws/l++21GLBlaZGVCBpXVpwTtXbHq5Wxfeqo1+xSMXXho oXL3juulRNAkPLLRsEUY+evXdLAjhCacrhHAqmBIkg72MIuRT9dhmN7F7w6NPXw0IANz 7GUD579qAdHCfwMx66K/WfRCBN8cGXbibX0Cl0ThQ5a4PZ/6gQwkLOHTCiBiEaHiVxzV RfvdEYBqqCMxoBBSelOR8YkMdMe/EQGIMDQiU0HBYQOOCeWI9L9ZKyJ9fQE+rp0VQ/c2 XddA== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Takashi Iwai Subject: [PATCH 4.9 04/67] ALSA: aloop: Sync stale timer before release Date: Tue, 27 Mar 2018 18:26:56 +0200 Message-Id: <20180327162726.923448202@linuxfoundation.org> X-Mailer: git-send-email 2.16.3 In-Reply-To: <20180327162726.702411083@linuxfoundation.org> References: <20180327162726.702411083@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1596108966146987882?= X-GMAIL-MSGID: =?utf-8?q?1596109099745964650?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai commit 67a01afaf3d34893cf7d2ea19b34555d6abb7cb0 upstream. The aloop driver tries to stop the pending timer via timer_del() in the trigger callback and in the close callback. The former is correct, as it's an atomic operation, while the latter expects that the timer gets really removed and proceeds the resource releases after that. But timer_del() doesn't synchronize, hence the running timer may still access the released resources. A similar situation can be also seen in the prepare callback after trigger(STOP) where the prepare tries to re-initialize the things while a timer is still running. The problems like the above are seen indirectly in some syzkaller reports (although it's not 100% clear whether this is the only cause, as the race condition is quite narrow and not always easy to trigger). For addressing these issues, this patch adds the explicit alls of timer_del_sync() in some places, so that the pending timer is properly killed / synced. Cc: Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/drivers/aloop.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/sound/drivers/aloop.c +++ b/sound/drivers/aloop.c @@ -192,6 +192,11 @@ static inline void loopback_timer_stop(s dpcm->timer.expires = 0; } +static inline void loopback_timer_stop_sync(struct loopback_pcm *dpcm) +{ + del_timer_sync(&dpcm->timer); +} + #define CABLE_VALID_PLAYBACK (1 << SNDRV_PCM_STREAM_PLAYBACK) #define CABLE_VALID_CAPTURE (1 << SNDRV_PCM_STREAM_CAPTURE) #define CABLE_VALID_BOTH (CABLE_VALID_PLAYBACK|CABLE_VALID_CAPTURE) @@ -326,6 +331,8 @@ static int loopback_prepare(struct snd_p struct loopback_cable *cable = dpcm->cable; int bps, salign; + loopback_timer_stop_sync(dpcm); + salign = (snd_pcm_format_width(runtime->format) * runtime->channels) / 8; bps = salign * runtime->rate; @@ -745,7 +752,7 @@ static int loopback_close(struct snd_pcm struct loopback *loopback = substream->private_data; struct loopback_pcm *dpcm = substream->runtime->private_data; - loopback_timer_stop(dpcm); + loopback_timer_stop_sync(dpcm); mutex_lock(&loopback->cable_lock); free_cable(substream); mutex_unlock(&loopback->cable_lock);