From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D2EDB17E8F5; Mon, 27 May 2024 19:00:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716836403; cv=none; b=cpUXOW4wYGsZyyZXqseFbd+lm6XzwVGbzfaxZvQXrTWRikCb2QB77JHGhw0kTpEgnqsdg4s92bjX6fKE3KeilP0uOHDX2xSnwkKxzC9moh8hDtjyEKhaHimY2xRuabRdcJ29DVHJ7j5K73btd+K4H1dys76H1twftw9RcDERpIQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716836403; c=relaxed/simple; bh=lJHyrgezMFoNID80NhIdK7Vspcb0jsUBhaWSGmJOrW0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BAZmYk++cfXrcnboiE/lUmW/gOw17h8ME4kn15jdzU+Y+h+hz28/hhQ1+uSn6TKitiD9in7OK5DsopOE+2aH3oXE5XwEklJIPznb1C1trOF4UCECGYoxMN8631ELzMC6q3nr4kAoMnujJDaHsArBGjvWCc81A5ZzRX0pbnUItTw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qLGTW0QV; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="qLGTW0QV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 67CAAC2BBFC; Mon, 27 May 2024 19:00:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1716836403; bh=lJHyrgezMFoNID80NhIdK7Vspcb0jsUBhaWSGmJOrW0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qLGTW0QVBItL54fRdBHWpnfmevTZfB/YGYf9G9Gg7cNSq61oecZ71t1dGAzFS8gBm 7eld+qU04GAbxQqlWHDQRhz+36P43XgX5+zAT18PuSQqC/pHc7vu1czsYK4fw2IE6q CXAtjcAaF4HivbpAGR9tCUO+nR7rX04k7NfFnpME= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+43120c2af6ca2938cc38@syzkaller.appspotmail.com, Takashi Iwai Subject: [PATCH 6.9 039/427] ALSA: timer: Set lower bound of start tick time Date: Mon, 27 May 2024 20:51:26 +0200 Message-ID: <20240527185605.328089202@linuxfoundation.org> X-Mailer: git-send-email 2.45.1 In-Reply-To: <20240527185601.713589927@linuxfoundation.org> References: <20240527185601.713589927@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai commit 4a63bd179fa8d3fcc44a0d9d71d941ddd62f0c4e upstream. Currently ALSA timer doesn't have the lower limit of the start tick time, and it allows a very small size, e.g. 1 tick with 1ns resolution for hrtimer. Such a situation may lead to an unexpected RCU stall, where the callback repeatedly queuing the expire update, as reported by fuzzer. This patch introduces a sanity check of the timer start tick time, so that the system returns an error when a too small start size is set. As of this patch, the lower limit is hard-coded to 100us, which is small enough but can still work somehow. Reported-by: syzbot+43120c2af6ca2938cc38@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/000000000000fa00a1061740ab6d@google.com Cc: Link: https://lore.kernel.org/r/20240514182745.4015-1-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/timer.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -544,6 +544,14 @@ static int snd_timer_start1(struct snd_t SNDRV_TIMER_IFLG_START)) return -EBUSY; + /* check the actual time for the start tick; + * bail out as error if it's way too low (< 100us) + */ + if (start) { + if ((u64)snd_timer_hw_resolution(timer) * ticks < 100000) + return -EINVAL; + } + if (start) timeri->ticks = timeri->cticks = ticks; else if (!timeri->cticks)