From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 74D4D3CB911; Wed, 30 Sep 2026 06:29:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790749765; cv=none; b=hbTUVZdCeg/IIuE7mG3jBIQywyL3KTK1gBYM2fyYUlCBr45xwj1xp8kXvE1SJ7fvfnu9wuBzF0qZesomQgYXYs3xVTu9lAKKzOVGVJUw61VbM2U8pfoeFfW60EOhEsWQJbhk9MAif2mNluVNlLdMgCO3cOnZkonfrs6pU1/eKMI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790749765; c=relaxed/simple; bh=AwDISh0R+fHyeXxhdGxKT/0v0ExobweT9FmrBs84tQw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=JMaLIB20S4A0/Yd3Zrr4RUhIXE1k79NRTh6RYz69SgePjSieVwfhCIFl+Q8+CjPy2STDaiyO9LLTGAI16/VHWJD/sqnd9T+ezEye2TCDdbD32o0j8fB7OKhI1jYKTlLLB6vFayguSipIFxuqvey8UZuY8vhUBHYHkMtOhQl+VSA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hsJZ/4fx; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hsJZ/4fx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 12EAD1F00893; Wed, 30 Sep 2026 06:29:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790749751; bh=DWRtKNH1nxh/OEl7iilUD04E3DvVNPsnEInVOWNPThw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=hsJZ/4fxtj9GyWu475jOm3YTEn5zgoBUBFJjAtq59gNzLbCt0Ow2EG1aJyeGkDCkM /P2DIYpaq+QnBB3KwC5i0NobeJV7isWz2v2M/0e720QTKTVmv8xxtuoqmueP6Q2b43 uhXtiwedWrw5oKYDjihhG5hnAeXB9nL9Z84TWXsfjt7ZS7nTFBrtG2/dlqay6W9OGL SShrQkt3SZriitTM7tIwJfF9A6yRYu8RWRnEVfRt7n4LRVlUgAy+YQ4xPbolXL9Z4Z 4fBUAyM1n6rqBw00y1+fWc6DIbWt9g+SZgARGeBEPUBzlRhCJHoaKt8+j2h7c0FYDU Yx4yNNJda2I6Q== Message-ID: Date: Wed, 30 Sep 2026 08:29:07 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 3/3] serial: core: reject baud_base values that overflow port->uartclk in uart_set_info() To: Hui Peng , Greg Kroah-Hartman , John Ogness , =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= Cc: Andy Shevchenko , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260930041216.155911-1-benquike@gmail.com> <20260930041216.155911-4-benquike@gmail.com> Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 30. 09. 26, 6:12, Hui Peng wrote: > In uart_set_info(), new_info->baud_base is multiplied by 16 and stored in > uport->uartclk (an unsigned int): > > uport->uartclk = new_info->baud_base * 16; > > While uart_set_info() checks if (uartclk == 0) and > if (new_info->baud_base < 9600), when new_info->baud_base exceeds > UINT_MAX / 16 with low bits set (for example, 0x10000001), multiplying > by 16 wraps around in 32-bit unsigned arithmetic to a small non-zero value > (16), bypassing both uartclk == 0 and new_info->baud_base < 9600 and > setting uport->uartclk = 16 (baud_base = 1, well below the required > minimum of 9600 * 16). > > Reject new_info->baud_base > UINT_MAX / 16 before multiplying by 16 in > uart_set_info(). > > Tested in QEMU against Linux 7.3.0-rc3 by calling ioctl(fd, TIOCSSERIAL, > &ss) with ss.baud_base = 0x10000001 on /dev/ttyS1: on the unfixed kernel > TIOCSSERIAL succeeds (ret = 0) and wraps uport->uartclk to 16 > (TIOCGSERIAL reports baud_base = 1), whereas with the fix applied > TIOCSSERIAL returns -EINVAL and preserves the existing uport->uartclk. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Fixes: 6eabce6608d6 ("serial: core: check uartclk for zero to avoid divide by zero") > Cc: stable@vger.kernel.org > Reviewed-by: Ilpo Järvinen > Assisted-by: LLM > Signed-off-by: Hui Peng > --- > Changes in v5: > - Collect Reviewed-by from Ilpo Järvinen. > - Re-send as part of v5 series in a fresh standalone thread per Andy > Shevchenko's feedback. > > Changes in v4: > - Check new_info->baud_base > UINT_MAX / 16 before multiplying by 16, > as suggested by Ilpo Järvinen. > > Changes in v3: > - Add missing #include for UINT_MAX and move the > new_info->baud_base > UINT_MAX / 16 check to the uartclk == 0 check, as > suggested by Ilpo Järvinen. > > drivers/tty/serial/serial_core.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c > index 95774b0f1484..75bb1eaa27e7 100644 > --- a/drivers/tty/serial/serial_core.c > +++ b/drivers/tty/serial/serial_core.c > @@ -16,6 +16,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -931,8 +932,13 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port, > old_custom_divisor = uport->custom_divisor; > > if (!(uport->flags & UPF_FIXED_PORT)) { > - unsigned int uartclk = new_info->baud_base * 16; > + unsigned int uartclk; > + > /* check needs to be done here before other settings made */ > + if (new_info->baud_base > UINT_MAX / 16) > + return -EINVAL; > + > + uartclk = new_info->baud_base * 16; check_mul_overflow() instead? > if (uartclk == 0) > return -EINVAL; > } -- js suse labs