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=1794047664; b=ugmiRMlkkWpHI8jE1ZqPx9T6TuyVlFd5f2DUovQxaiqoYRv4aRdTR/3/bM6AbRBBvjXe cgc07RnvbID/a4AEG2/v+ByXQlPLQ/URAgBN+Ng8KNu3TV9BHWFFKjKT+45oQgbaqq5/K S6Z7ENcVeRUPI3bshMBeCYhfPX25jd3i76wA+Bw7FyR4Q5ywIdrXvcumEHw22wKwtr7lZ 8+P97sTYRsty0MCkUEpU1LLVAqY971peMkjh16YuNwuqifj1CUqwdAwslPIZbugtP9l5D AOr9GUFIpOF8XJW6iw/in0FDLT9IWgej31H5vMQjful1p6xmcSDRIr1J0H6cfCzDUaA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794047664; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=OtrqpVA6Jzs/AD+MBNJiyiP6Ca6Wi3qXYisZTPlRins=; b=aChRdIXEQyrVM25guXzdLqPG/Up5UZUINzALUpIJRQ6m4DcrPDrzdapx+4WjGaiHy76C dH9SAcKEgQSHo5xk2zp73BLBXC30SMCQdzhEp40p/4fmHofIVAH/LP5a5SqtjKrUtTx/f Y3aW00C8gtFyf5Y6PnrjsSOwLyBKFfcOoOcjCXoDOKjG8CYs6pD+OrFYqpm452qYTkt5p lbwhbXUMgxk9KUkzjaornbC+HH4jtHxFxekfP9MYYNRIpYa/90FY4iCiNfdHw1ERoffBO in4rgtvWEOnizg4L7/xckCGshRXwAlDEvq+kXEBEMaKzCEQ3m1RxVEsky+/tBTnne4w== 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=iioPBKHv; 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 CF705606A326 for ; Sat, 7 Nov 2026 10:34:23 +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=iioPBKHv Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4C4DA1F0089F; Sat, 7 Nov 2026 10:34:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794047663; bh=OtrqpVA6Jzs/AD+MBNJiyiP6Ca6Wi3qXYisZTPlRins=; h=From:To:Cc:Subject:Date; b=iioPBKHvWUI3NkUh2p8vYCRu2XZWAm4j9K3mlTDqU7KT1oxyAtjYPEz8TvYFtkLQR FTGpaCnG2VXI68ZcWscG+4g7FNDn2M2vPpDsZadI/2MiLN6upyaz0YpUA7ZxrFx8dA L0v5l1C08zDZ4mO3F9ZwYJaj5ekYrDkw8MRUwlDwMtKBGFyi2f9/b5VpK/jORbgEbB dB1JKzwp2LU6SY3dB9H3efLeA9vTh/CGV+Dobx9SrgB6sAzIPztSL4qBCwPe/xO9W+ crubyHOBjFMFTK6O4CXz1t86iPMSMc5Kbsjj/3Hh23TUV0BNoDcmlZGuNruz6NkVdr hgbXjHfeG1MWg== From: Sasha Levin To: martin.fuzzey@flowbird.group, gregkh@linuxfoundation.org Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] serial: sc16is7xx: fix data corruption due to unexpected xon/xoff" failed to apply to 6.6-stable tree Date: Sat, 7 Nov 2026 05:34:22 -0500 Message-ID: <20261107053422-failed-6.6-8bb50e95c0ab@kernel.org> X-Mailer: git-send-email 2.53.0 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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 8bb50e95c0abd44607bc60a43032c1dbf7470d5a # git commit -s git send-email --to '' --in-reply-to '20261107053422-failed-6.6-8bb50e95c0ab@kernel.org' --subject-prefix 'PATCH 6.6.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 8bb50e95c0abd44607bc60a43032c1dbf7470d5a Mon Sep 17 00:00:00 2001 From: Martin Fuzzey Date: Thu, 1 Oct 2026 10:05:35 +0000 Subject: [PATCH] serial: sc16is7xx: fix data corruption due to unexpected xon/xoff 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 --- 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 296079c16fdb9..7ddc8a38adab4 100644 --- a/drivers/tty/serial/sc16is7xx.c +++ b/drivers/tty/serial/sc16is7xx.c @@ -1516,7 +1516,7 @@ static int sc16is7xx_setup_channel(struct sc16is7xx_one *one, int i, /* Initialize port data */ port->type = PORT_SC16IS7XX; port->fifosize = SC16IS7XX_FIFO_SIZE; - port->flags = UPF_FIXED_TYPE | UPF_LOW_LATENCY; + port->flags = UPF_FIXED_TYPE | UPF_LOW_LATENCY | UPF_SOFT_FLOW; port->iotype = UPIO_BUS; port->rs485_config = sc16is7xx_config_rs485; port->rs485_supported = sc16is7xx_rs485_supported; -- 2.53.0