From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx4+pFkLNezDZCsBzNpEeREnz402FCwhpmuiUWc58Ne6gn8BBo7d+5nTJSr27d/zGVfqmUTTX ARC-Seal: i=1; a=rsa-sha256; t=1524406794; cv=none; d=google.com; s=arc-20160816; b=zdJNujpZ5xQmficy8dr/qUOJ68wG0+fr3N2QCEKWuiwA36di08siZKKIy1MGQ/CzWe TemUAbbixeiotTi+hh/Cek9QciVeWuVHo/jjvc2CABt75jflk/qld1kN1bA1/+e4IggS Z0sHcofyWecWnlyBu4x8edtCXCLC7Q3ay3rxuquKR00nzeF1dGLXC/hRjSkMwkGEwW6Z xtrFRGIxg/RTIaNRHFEn5762SPGV79f/+xDatgBajX4k4IN8F8h6btEH1vNoX4kpFytF xtT1ZS0zKZssXJJ7ERmMXKwILF9DggXGwDB2kdSdd7HJQ857FjoB5Rr2MwVFaaY8UiAH kW0A== 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=OhTD0/Ug0W6QiUDFSfY0tJVKI6hLGBD7KxFcxKV6UEg=; b=sRoZYKO6pLkDm0EHM/xSWZatoDRIhNZytilyXCYUraFdUprmgUvmt3DpWkh2unnrrd F5tle8DysvdZeMaUV/DrXkjjRHMSFGMjqcFqKGGMjJN6pg2hMAsv8rhl4y7yZxTffi6a dlSgg07Jx6m/jntIbyojettsWc+HYjuTOTnhedCNBLRc/QMMZ9O27hDBx/dayYsIJwUC 1MwHl3BSE7ZkZgkF1BtuZijv0xsrjvRPVv1ryjO1V0m670LhwLgEEJBDEbF4wNWagDm9 0hucyN7njRa/ArBlr2Rp9RmGhrK1IRcmseNOjh6GeVNctbrYalJeq8PCTtj+OddKk54D Dtgw== 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 4.4 70/97] ALSA: pcm: Fix endless loop for XRUN recovery in OSS emulation Date: Sun, 22 Apr 2018 15:53:48 +0200 Message-Id: <20180422135309.086919953@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180422135304.577223025@linuxfoundation.org> References: <20180422135304.577223025@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?1598456379178714339?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.4-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 @@ -1138,13 +1138,14 @@ 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,