From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx48OyretYtDnkbQo1zYpdXgB06sBINxIDk/ZPTpH4TzfQjI0P9s2g+x59aZ9m4rSRbOFk+c1 ARC-Seal: i=1; a=rsa-sha256; t=1524406872; cv=none; d=google.com; s=arc-20160816; b=gJAWd8DmI2I+aunQhgqz4k99gkODqqXDHliqsbWO5bigtVinyhsV8ZJMzIXWaGsueo cMNQdf7KOug/diqtoehZbLuiiJvRtdYXK/YwSqDV7ReykWW9MPpBJLEqgaM6SEy5WGBN 9zAcztogcg1VCS5GHesdC4xKKk2rPN3Dz7OgiZ1/t9NtPoc37G0h6kpMjvxw5HrNBtVD yM4Dgb5vVxJ/ofTvjWnae/wh+g+6Bh+kRzfJtqyJxrXRuriONMGLrjLzSrab4TjFFLdS 7dH6/uDRuCKH344mMReY0vWk0JsP5BE7+uMtnFpIz1+B/xdlbnSEVF/1C3bHi7voAgGP uokQ== 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=r+4KuXhB8ATOeI51nctZYZj9gNym8V8OPMUQS+8jwCU=; b=R42ZNIYFQYrQuKotvTzdIqvDZJtu39824FpK3WEyh4fwV3U90NJ+KSJNKaidAyJs0e ESHsyKK4jwekoi+FKq4ivJmGXsoNfQNPR8hAGfnebW25G+bEdrojgjN1KyasirZggJKc pvfEsyfFmzik5B0DBrIS77zJCqIJt4/wAt0jlScm1PJoMQQKL1jkTBK5mTdnPDAKzoDU 2uwlCpWHNCncB1xCglqwsRMByXcKwnZAIe8/9n77V9Pst3sgNuRzmGUjSODuKKP7Gn28 Ufn0e6q5ASw4knyKE8tDmSB200X4DKRlytd/yO9NbGzzxlZS74WY3ERTMKI9JWxjXiwu ItAw== 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, syzbot+150189c103427d31a053@syzkaller.appspotmail.com, syzbot+7e3f31a52646f939c052@syzkaller.appspotmail.com, syzbot+4f2016cf5185da7759dc@syzkaller.appspotmail.com, Takashi Iwai Subject: [PATCH 3.18 36/52] ALSA: pcm: Fix endless loop for XRUN recovery in OSS emulation Date: Sun, 22 Apr 2018 15:54:09 +0200 Message-Id: <20180422135317.083787173@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180422135315.254787616@linuxfoundation.org> References: <20180422135315.254787616@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?1598455089227122133?= X-GMAIL-MSGID: =?utf-8?q?1598456461244250113?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai commit e15dc99dbb9cf99f6432e8e3c0b3a8f7a3403a86 upstream. The commit 02a5d6925cd3 ("ALSA: pcm: Avoid potential races between OSS ioctls and read/write") split the PCM preparation code to a locked version, and it added a sanity check of runtime->oss.prepare flag along with the change. This leaded to an endless loop when the stream gets XRUN: namely, snd_pcm_oss_write3() and co call snd_pcm_oss_prepare() without setting runtime->oss.prepare flag and the loop continues until the PCM state reaches to another one. As the function is supposed to execute the preparation unconditionally, drop the invalid state check there. The bug was triggered by syzkaller. Fixes: 02a5d6925cd3 ("ALSA: pcm: Avoid potential races between OSS ioctls and read/write") Reported-by: syzbot+150189c103427d31a053@syzkaller.appspotmail.com Reported-by: syzbot+7e3f31a52646f939c052@syzkaller.appspotmail.com Reported-by: syzbot+4f2016cf5185da7759dc@syzkaller.appspotmail.com Cc: Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/oss/pcm_oss.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/sound/core/oss/pcm_oss.c +++ b/sound/core/oss/pcm_oss.c @@ -1139,13 +1139,14 @@ static int snd_pcm_oss_get_active_substr } /* call with params_lock held */ +/* NOTE: this always call PREPARE unconditionally no matter whether + * runtime->oss.prepare is set or not + */ static int snd_pcm_oss_prepare(struct snd_pcm_substream *substream) { int err; struct snd_pcm_runtime *runtime = substream->runtime; - if (!runtime->oss.prepare) - return 0; err = snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_PREPARE, NULL); if (err < 0) { pcm_dbg(substream->pcm,