From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794336020; b=U15GhuBsQLsjAzgkQ0h4Vx6vAUEupr54ufX7lAQr4mdkd0Dv+Y4rsTiFB+yOepWyipxE 0Hla/XH/Npfz1fvS8wiydDmyaZrrt5d/Sk4I45CCyTykhv0DGfzt8JBkzIn6npWH2Ht7q UPPCgCoapgNsHO4nKWU0SQjbm0ql6PQ6CUPLM9y7qEMk1xVX5ui08RDRV7Th9mOp189ZK oMy0/1TPhjHasaE35ux6cAoq3ch652OXpgoWiYPL9Ue6P9+KcQXSChHXXODWJ1ykuvSUm /5RyjD3N2yI446cXtT4+6UHJPrWAxfS+DDzyrsrUuEZp8RUmtdRJbuHkgMjlU3OUL8g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794336020; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=NX8Bgqj1cYflPJDUmwjJtPnSzWDqNwLdB/3DJANbDY0=; b=Dq9ibZ5y9Nbt52+dRTNvHTafq7pewdgU5QumCaozOsL2KrghdzHwEkz2fOT+xxVZdpxA LpainLcWG2Nqj2xqDJHBaFm0ToUMi2KBS/d6oL++XyLeauScgJu4tZLcLfFxZlUMELCWo wKqJXECqK2gZzw28LYOAQSRFi0sCOQjWCkJue57Yr8DxmokFIwtTkCZLpD1hb5dnulEnp lvW7zq72UpEUqWmjxp3ZgyTQ6V91yjbYebcSvtLL97D8XeO4E3IgLkNxpy4GY4z5XrKaR nc5dwB6Q56ItIdOns9xokOLG04NDu3Y7LO0CKqCPGPwkL6fkVn/IMKxF1qdRoFbvrTA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=TNEHW8Dh; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C6A9960A260C for ; Tue, 10 Nov 2026 18:40:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=TNEHW8Dh Received: by smtp.kernel.org (Postfix) with ESMTPSA id C31B21F0089F; Tue, 10 Nov 2026 18:40:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794336019; bh=NX8Bgqj1cYflPJDUmwjJtPnSzWDqNwLdB/3DJANbDY0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=TNEHW8Dhp9KY/5lKuo0uqb46nt9CBA03HGfjMnQ5V+90gZxrwOprCiQChp/yuO2We HDAhaD3fXkPGzeV5ZQiRJhTsjq6wX0OZ11mlqKEMaVOKrvqwYHnj9DGbWjm04n8CYe yKuP1etJpb3VfegsgZ9h4tBd6WVJIb69+MYSKcwFpxx2Ism3P6M/jThiB1MIKV40Tq A+nuCd4Jzvvv1yGx/+0lOSAv1SROXEIrfGBVvbX7qI5PMZ0DXHYlEOpTKVnnFa846W fb8Hx3XixD9neKmF9cOhMhk1W+RAvzoNdIeFm64y/U+TKvYuGMG3amW7ZSLw6vhMkK hxTCGyY+dhr5Q== From: Sasha Levin To: stable@vger.kernel.org Cc: Martin Fuzzey , stable@kernel.org, Greg Kroah-Hartman , Sasha Levin Subject: [PATCH 6.12.y] serial: sc16is7xx: fix data corruption due to unexpected xon/xoff Date: Tue, 10 Nov 2026 13:40:17 -0500 Message-ID: <20261110183856.3306633-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107052156-failed-6.12-8bb50e95c0ab@kernel.org> References: <20261107052156-failed-6.12-8bb50e95c0ab@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Martin Fuzzey [ Upstream commit 8bb50e95c0abd44607bc60a43032c1dbf7470d5a ] The hardware supports automatically sending XON/OFF based on the FIFO status and that is already implemented by the driver. However that capability was not announced with the UPF_SOFT_FLOW bit. When the port is opened with the default of XON enabled the driver configures that in the hardware. If userspace does not want XON/OFF (which is normally the case) it will use TCSETS to disactivate it. However the serial core optimises this to only notify the driver if someting imporant has changed, and for XON/XOFF thit is only if the driver declares UPF_SOFT_FLOW. So we end up with unwanted XON/XOFF in the data stream. The problem only occurs if nothing else needed to be set by termios, ie if the user space requested values are the same as the default values, except for XON/XOFF. Since the default speed is 9600 this means that the problem only occurs when requesting 9600, otherwise the call to the driver will be made to change the speed, and that will also clear the XON/XOFF. As 9600 is quite rare these days that probably explains why this hasn't already been seen. It also only occurs on the first port open after boot since the subsequent opens will use the "logical state" set by TCSETS but not communicated to the driver the first time. Signed-off-by: Martin Fuzzey Fixes: dfeae619d781 ("serial: sc16is7xx") Cc: stable@kernel.org Link: https://patch.msgid.link/20261001100534.1225894-1-martin.fuzzey@flowbird.group Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/sc16is7xx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c index 942d12f40a394..2c33c053beff2 100644 --- a/drivers/tty/serial/sc16is7xx.c +++ b/drivers/tty/serial/sc16is7xx.c @@ -1615,7 +1615,7 @@ int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype, s->p[i].port.irq = irq; s->p[i].port.type = PORT_SC16IS7XX; s->p[i].port.fifosize = SC16IS7XX_FIFO_SIZE; - s->p[i].port.flags = UPF_FIXED_TYPE | UPF_LOW_LATENCY; + s->p[i].port.flags = UPF_FIXED_TYPE | UPF_LOW_LATENCY | UPF_SOFT_FLOW; s->p[i].port.iobase = i; /* * Use all ones as membase to make sure uart_configure_port() in -- 2.53.0