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 5E8FC182B4; Thu, 31 Jul 2025 07:43:42 +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=1753947822; cv=none; b=qd7DiQuzXVviY/k0oFGyGBpjxuU9Bw7CdX/5ronox+SJ+tuCXlHIExCffMS4gSN+JB3c/xLVIH5n/BNc8x5nQlNsqJuBljVNwU11vOLpJAdNTXwSPlQGz0OPPxRWASm1vear1KaiJuaqqZa1HB71R5IX+WSqNAqSCIa35K1OaCc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753947822; c=relaxed/simple; bh=dfkxlAhth0XmEKtbUibM0ahNPbD745YG3XeVC3p4lnc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=B4ZP99YCNfbhUCY1piUjh5YYxIvMKw29vdLGRGMYPUSNZmQUDTF1maxqi+YRLOc+uZNGkbxzPS7fYMm3k5NWRBBC8wiUlNsMFAhNO+L6bfJpIZ1qzDYTq4LFqM+GLhv1vxqoCD3OA33efASF1i6fgSBSXYCzgLO9nR4rG9RPlIs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=o8IjCfbs; 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="o8IjCfbs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A11B7C4CEEF; Thu, 31 Jul 2025 07:43:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1753947821; bh=dfkxlAhth0XmEKtbUibM0ahNPbD745YG3XeVC3p4lnc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=o8IjCfbs1pNofaCmeDZ7T6nO6psFfbn91KBp5/3PThlMAVdRTMo4WWuqzbXzs2OFo WM9xYQz/afLQ3F56m9qRiLJkCYh5vZ83YEmXFremwDAzi6xa5u0eXmdCFxopHIwlXo ri0JYL/m6JRePkaU5wD6DlnCvRjKse/BCTndNd1pMsxrZjmIxsjHc6N2GP1MXFfTk9 0UPKe2obOOWrRnFtFs9MRwxFF1QYjXjRLyeX67X6oxIf8uyVN/iQeVnhovYnha1rpP d+23xcsXM5Extn24MzQWb8KPe0KjY3fCmpOu7Kli/Qzwvq4I4avyg0nVsJTAB0knFU 6Di8drWojC9zw== Message-ID: Date: Thu, 31 Jul 2025 09:43:38 +0200 Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] HID: multitouch: fix integer overflow in set_abs() To: Qasim Ijaz Cc: jikos@kernel.org, bentiss@kernel.org, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20250723173659.59327-1-qasdev00@gmail.com> <914ff45b-2260-42c0-9ccf-a3efd667d4f5@kernel.org> 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 24. 07. 25, 17:56, Qasim Ijaz wrote: > On Thu, Jul 24, 2025 at 08:58:40AM +0200, Jiri Slaby wrote: >> On 23. 07. 25, 19:36, Qasim Ijaz wrote: >>> It is possible for a malicious HID device to trigger a signed integer >>> overflow (undefined behaviour) in set_abs() in the following expression >>> by supplying bogus logical maximum and minimum values: >>> >>> int fuzz = snratio ? (fmax - fmin) / snratio : 0; >>> >>> For example, if the logical_maximum is INT_MAX and logical_minimum is -1 >>> then (fmax - fmin) resolves to INT_MAX + 1, which does not fit in a 32-bit >>> signed int, so the subtraction overflows. >> >> The question is if it matters with -fwrapv? > > Ah yea thanks for bringing this up Jiri. I think you might be correct, > after doing some research it looks like the kernel enables -fno‑strict‑overflow > which implies -fwrapv which leads to wrap around instead of UB If I undestand > correctly. So with that in mind this patch probably doesn't do anything > useful, do you agree? Yes, it correctly wraps around. But the question remains :). Does it matter or not? thanks, -- js suse labs