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 958DF2BE051; Thu, 20 Nov 2025 07:23:25 +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=1763623405; cv=none; b=CHjtvMGFEPcRJi7xn2xfiHc7RiI1tgSxZlrJYT7NJXmJ5RvBlEP2xl1GEODtMpTuCtH7V/W4FMQGdsDlaJeh4MIwcY4RvSKGN+W6S07Trk2vW5qzwkOG4ji5z4K2g6358KRWMYtTFKvCCeImgwc7LFQTWYGOGRARLM90LAgq6Wg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763623405; c=relaxed/simple; bh=JGUDOC99Te7uT9oGz4nOziqcBw4DJfb6MAr2dLTFbi0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=i9cBEeqwIz2WPuGTseOKCih2lKWiRKXBzxYw3fgjByS9Z89OZ9yFiq5lxP2xtId05/BtbyTJ8PCngfu9LRcRF+1CywpEbwBnIkEcm+sydisofdj2ZOcq38Jxmwy7/lnKvQHH8IiGxmjoPvFh8+F7W+UxVNO23U0OBC4d7MZyIVE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=uMfBE3hb; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="uMfBE3hb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 50CC9C4CEF1; Thu, 20 Nov 2025 07:23:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763623405; bh=JGUDOC99Te7uT9oGz4nOziqcBw4DJfb6MAr2dLTFbi0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=uMfBE3hbbyth0PB22bzyAq9WQVmlAQTVQReLXb/Wy5jjiH+m9yWJIAkUC16ZdYVwc 11MDXPwKkkRpcBMwz0OHJQDTt2WdlFhoyk04c3lKllPL33oDZ9up0FSpPm0PlSVS0G QhFFCH3AFqtrAXd/Vi3ncI8jEiDikNzSeq8tgjXYJEHAHbpm3POQSeRxW1WVbIgDX0 pHL7VJZ1XITBZ7nP/hDqUDyMIvIkgWdBbehedVh3PQNJdC7mzZWJY0ISlnHrXz7xXG 0UKAzh7de/woeFIt878ozutXsQN5w5/7vS6gIEPMSqq7Pd634+3dd0JXmPArvlVh8S fajj1pDGSf99A== Message-ID: Date: Thu, 20 Nov 2025 08:23:22 +0100 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 27/44] drivers/tty/vt: use umin() instead of min_t(u16, ...) for row/col limits To: david.laight.linux@gmail.com, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org Cc: Greg Kroah-Hartman References: <20251119224140.8616-1-david.laight.linux@gmail.com> <20251119224140.8616-28-david.laight.linux@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: 7bit On 19. 11. 25, 23:41, david.laight.linux@gmail.com wrote: > From: David Laight > > The row/column bounds (for a screen window box) are changed from > 'offset one' to 'offset zero' and bound to the screen size using: > v->xs = min_t(u16, v->xs - 1, vc->vc_cols - 1); > This has the side effect of converting zero to the limit. > > A check I'm adding to min_t() reports that (u16)(v->xs - 1) (etc) > discards signiticant bits (because v->xs is promoted to 'int' before > the addition). > If v->xs is zero (it comes from userspace) it converts -1 to 0xffff. > This is then bounded to 'vc->vc_cols - 1' which will be fine. > > Replace with: > v->xs = umin(v->xs - 1, vc->vc_cols - 1); > which again converts a -1 to unsigned - this time to 0xffffffff, > with the same overall effect. LGTM: Reviewed-by: Jiri Slaby > Whether zero is meant to mean the 'maximum size' is unknown. > I can't find any documentation for the ioctl and it pre-dates git. Behavior of zero is unspecified AFAICT (the impl can do whatever is easy :)). thanks, -- js suse labs