From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AB42ECDB474 for ; Mon, 16 Oct 2023 05:35:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231623AbjJPFfS (ORCPT ); Mon, 16 Oct 2023 01:35:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45906 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231783AbjJPFfO (ORCPT ); Mon, 16 Oct 2023 01:35:14 -0400 Received: from mail-wm1-f42.google.com (mail-wm1-f42.google.com [209.85.128.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B16AE120; Sun, 15 Oct 2023 22:35:05 -0700 (PDT) Received: by mail-wm1-f42.google.com with SMTP id 5b1f17b1804b1-405497850dbso41234255e9.0; Sun, 15 Oct 2023 22:35:05 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1697434504; x=1698039304; h=content-transfer-encoding:in-reply-to:autocrypt:from:references:cc :to:content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=cOvvTQQy+JfGRbCEkEtFd8cZk3x1MPjZLKQ8b9QGiKU=; b=d8pASWNRWlheRT/OCvXdBIC3LJQoEiBKaaRv8pURKL3lQg2g4GKjLQkQg4dbzfQTnL j7EoHln3Er1wOQwbvjVEKRWpYp3YJJDo9Rv3E7v05QZqbSahRlRkiagy3tBvobbwNCRU 7a+4X2FHN3g6dgzDULM58roEbv66kQkq7xR579YfFzoZvWMQIhNMVkEThWHoOJMl9N2y CayQWpBlsKHyw5NpPW//MiY8B9SEnoj7Mha4WRxSfXmTrttFmfr/rQZ5lsZqQdYlQI8I PmKozCOMSMBLFiHo2FXK39B96ryy0aGdvggEoHx6s5HezOuP5aGK0RsEh9Z8FskKuEqK UT2w== X-Gm-Message-State: AOJu0YxYMfmoHf/957hE2kww/LsvsxT2/Pp6QDUB1UINGeygHLu5ofM8 cLZzhbgXkuDa1DsPR4Al4chhXsnJEqk= X-Google-Smtp-Source: AGHT+IFPZe+piZQPNHSWAA8zt7wf5lSfRigoQiafEWSLJwRkAESEX8SvLMO4dQgrZTTnxw5TiwCvnA== X-Received: by 2002:a05:600c:2197:b0:405:514d:eb0e with SMTP id e23-20020a05600c219700b00405514deb0emr28704305wme.19.1697434503719; Sun, 15 Oct 2023 22:35:03 -0700 (PDT) Received: from ?IPV6:2a0b:e7c0:0:107::aaaa:59? ([2a0b:e7c0:0:107::aaaa:59]) by smtp.gmail.com with ESMTPSA id t14-20020a05600c198e00b00405c7591b09sm6161011wmq.35.2023.10.15.22.35.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 15 Oct 2023 22:35:03 -0700 (PDT) Message-ID: <0d5f9af2-22ac-4753-8c5a-76c4d44dcc9c@kernel.org> Date: Mon, 16 Oct 2023 07:35:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/3] serial: core: Potential overflow of frame_time Content-Language: en-US To: Vamshi Gajjela , Greg Kroah-Hartman , ilpo.jarvinen@linux.intel.com Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, manugautam@google.com, Subhash Jadavani , Channa Kadabi References: <20231014181333.2579530-1-vamshigajjela@google.com> From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; keydata= xsFNBE6S54YBEACzzjLwDUbU5elY4GTg/NdotjA0jyyJtYI86wdKraekbNE0bC4zV+ryvH4j rrcDwGs6tFVrAHvdHeIdI07s1iIx5R/ndcHwt4fvI8CL5PzPmn5J+h0WERR5rFprRh6axhOk rSD5CwQl19fm4AJCS6A9GJtOoiLpWn2/IbogPc71jQVrupZYYx51rAaHZ0D2KYK/uhfc6neJ i0WqPlbtIlIrpvWxckucNu6ZwXjFY0f3qIRg3Vqh5QxPkojGsq9tXVFVLEkSVz6FoqCHrUTx wr+aw6qqQVgvT/McQtsI0S66uIkQjzPUrgAEtWUv76rM4ekqL9stHyvTGw0Fjsualwb0Gwdx ReTZzMgheAyoy/umIOKrSEpWouVoBt5FFSZUyjuDdlPPYyPav+hpI6ggmCTld3u2hyiHji2H cDpcLM2LMhlHBipu80s9anNeZhCANDhbC5E+NZmuwgzHBcan8WC7xsPXPaiZSIm7TKaVoOcL 9tE5aN3jQmIlrT7ZUX52Ff/hSdx/JKDP3YMNtt4B0cH6ejIjtqTd+Ge8sSttsnNM0CQUkXps w98jwz+Lxw/bKMr3NSnnFpUZaxwji3BC9vYyxKMAwNelBCHEgS/OAa3EJoTfuYOK6wT6nadm YqYjwYbZE5V/SwzMbpWu7Jwlvuwyfo5mh7w5iMfnZE+vHFwp/wARAQABzSFKaXJpIFNsYWJ5 IDxqaXJpc2xhYnlAa2VybmVsLm9yZz7CwXcEEwEIACEFAlW3RUwCGwMFCwkIBwIGFQgJCgsC BBYCAwECHgECF4AACgkQvSWxBAa0cEnVTg//TQpdIAr8Tn0VAeUjdVIH9XCFw+cPSU+zMSCH eCZoA/N6gitEcnvHoFVVM7b3hK2HgoFUNbmYC0RdcSc80pOF5gCnACSP9XWHGWzeKCARRcQR 4s5YD8I4VV5hqXcKo2DFAtIOVbHDW+0okOzcecdasCakUTr7s2fXz97uuoc2gIBB7bmHUGAH XQXHvdnCLjDjR+eJN+zrtbqZKYSfj89s/ZHn5Slug6w8qOPT1sVNGG+eWPlc5s7XYhT9z66E l5C0rG35JE4PhC+tl7BaE5IwjJlBMHf/cMJxNHAYoQ1hWQCKOfMDQ6bsEr++kGUCbHkrEFwD UVA72iLnnnlZCMevwE4hc0zVhseWhPc/KMYObU1sDGqaCesRLkE3tiE7X2cikmj/qH0CoMWe gjnwnQ2qVJcaPSzJ4QITvchEQ+tbuVAyvn9H+9MkdT7b7b2OaqYsUP8rn/2k1Td5zknUz7iF oJ0Z9wPTl6tDfF8phaMIPISYrhceVOIoL+rWfaikhBulZTIT5ihieY9nQOw6vhOfWkYvv0Dl o4GRnb2ybPQpfEs7WtetOsUgiUbfljTgILFw3CsPW8JESOGQc0Pv8ieznIighqPPFz9g+zSu Ss/rpcsqag5n9rQp/H3WW5zKUpeYcKGaPDp/vSUovMcjp8USIhzBBrmI7UWAtuedG9prjqfO wU0ETpLnhgEQAM+cDWLL+Wvc9cLhA2OXZ/gMmu7NbYKjfth1UyOuBd5emIO+d4RfFM02XFTI t4MxwhAryhsKQQcA4iQNldkbyeviYrPKWjLTjRXT5cD2lpWzr+Jx7mX7InV5JOz1Qq+P+nJW YIBjUKhI03ux89p58CYil24Zpyn2F5cX7U+inY8lJIBwLPBnc9Z0An/DVnUOD+0wIcYVnZAK DiIXODkGqTg3fhZwbbi+KAhtHPFM2fGw2VTUf62IHzV+eBSnamzPOBc1XsJYKRo3FHNeLuS8 f4wUe7bWb9O66PPFK/RkeqNX6akkFBf9VfrZ1rTEKAyJ2uqf1EI1olYnENk4+00IBa+BavGQ 8UW9dGW3nbPrfuOV5UUvbnsSQwj67pSdrBQqilr5N/5H9z7VCDQ0dhuJNtvDSlTf2iUFBqgk 3smln31PUYiVPrMP0V4ja0i9qtO/TB01rTfTyXTRtqz53qO5dGsYiliJO5aUmh8swVpotgK4 /57h3zGsaXO9PGgnnAdqeKVITaFTLY1ISg+Ptb4KoliiOjrBMmQUSJVtkUXMrCMCeuPDGHo7 39Xc75lcHlGuM3yEB//htKjyprbLeLf1y4xPyTeeF5zg/0ztRZNKZicgEmxyUNBHHnBKHQxz 1j+mzH0HjZZtXjGu2KLJ18G07q0fpz2ZPk2D53Ww39VNI/J9ABEBAAHCwV8EGAECAAkFAk6S 54YCGwwACgkQvSWxBAa0cEk3tRAAgO+DFpbyIa4RlnfpcW17AfnpZi9VR5+zr496n2jH/1ld wRO/S+QNSA8qdABqMb9WI4BNaoANgcg0AS429Mq0taaWKkAjkkGAT7mD1Q5PiLr06Y/+Kzdr 90eUVneqM2TUQQbK+Kh7JwmGVrRGNqQrDk+gRNvKnGwFNeTkTKtJ0P8jYd7P1gZb9Fwj9YLx jhn/sVIhNmEBLBoI7PL+9fbILqJPHgAwW35rpnq4f/EYTykbk1sa13Tav6btJ+4QOgbcezWI wZ5w/JVfEJW9JXp3BFAVzRQ5nVrrLDAJZ8Y5ioWcm99JtSIIxXxt9FJaGc1Bgsi5K/+dyTKL wLMJgiBzbVx8G+fCJJ9YtlNOPWhbKPlrQ8+AY52Aagi9WNhe6XfJdh5g6ptiOILm330mkR4g W6nEgZVyIyTq3ekOuruftWL99qpP5zi+eNrMmLRQx9iecDNgFr342R9bTDlb1TLuRb+/tJ98 f/bIWIr0cqQmqQ33FgRhrG1+Xml6UXyJ2jExmlO8JljuOGeXYh6ZkIEyzqzffzBLXZCujlYQ DFXpyMNVJ2ZwPmX2mWEoYuaBU0JN7wM+/zWgOf2zRwhEuD3A2cO2PxoiIfyUEfB9SSmffaK/ S4xXoB6wvGENZ85Hg37C7WDNdaAt6Xh2uQIly5grkgvWppkNy4ZHxE+jeNsU7tg= In-Reply-To: <20231014181333.2579530-1-vamshigajjela@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14. 10. 23, 20:13, Vamshi Gajjela wrote: > From: VAMSHI GAJJELA > > uart_update_timeout() sets a u64 value to an unsigned int frame_time. > While it can be cast to u32 before assignment, there's a specific case > where frame_time is cast to u64. Since frame_time consistently > participates in u64 arithmetic, its data type is converted to u64 to > eliminate the need for explicit casting. And make the divisions by the order of magnutude slower for no good reason? (Hint: have you looked what DIV64_U64_ROUND_UP() looks like on 32bit yet?) Unless you provide a reason it can overflow in real (in fact you spell the opposite in the text above): NACKED-by: Jiri Slaby > Signed-off-by: VAMSHI GAJJELA > --- > v2: > - use DIV64_U64_ROUND_UP with frame_time > > drivers/tty/serial/8250/8250_port.c | 2 +- > include/linux/serial_core.h | 4 ++-- > 2 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c > index 141627370aab..d1bf794498c4 100644 > --- a/drivers/tty/serial/8250/8250_port.c > +++ b/drivers/tty/serial/8250/8250_port.c > @@ -1510,7 +1510,7 @@ static inline void __stop_tx(struct uart_8250_port *p) > * rather than after it is fully sent. > * Roughly estimate 1 extra bit here with / 7. > */ > - stop_delay = p->port.frame_time + DIV_ROUND_UP(p->port.frame_time, 7); > + stop_delay = p->port.frame_time + DIV64_U64_ROUND_UP(p->port.frame_time, 7); > } > > __stop_tx_rs485(p, stop_delay); > diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h > index bb6f073bc159..b128513b009a 100644 > --- a/include/linux/serial_core.h > +++ b/include/linux/serial_core.h > @@ -558,7 +558,7 @@ struct uart_port { > > bool hw_stopped; /* sw-assisted CTS flow state */ > unsigned int mctrl; /* current modem ctrl settings */ > - unsigned int frame_time; /* frame timing in ns */ > + unsigned long frame_time; /* frame timing in ns */ > unsigned int type; /* port type */ > const struct uart_ops *ops; > unsigned int custom_divisor; > @@ -764,7 +764,7 @@ unsigned int uart_get_divisor(struct uart_port *port, unsigned int baud); > */ > static inline unsigned long uart_fifo_timeout(struct uart_port *port) > { > - u64 fifo_timeout = (u64)READ_ONCE(port->frame_time) * port->fifosize; > + u64 fifo_timeout = READ_ONCE(port->frame_time) * port->fifosize; > > /* Add .02 seconds of slop */ > fifo_timeout += 20 * NSEC_PER_MSEC; -- js suse labs