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 DA71933E345 for ; Thu, 2 Apr 2026 17:58:46 +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=1775152726; cv=none; b=rEihkeoxqD4oOGXN1Jf0xnZv3Gj6wEXYl4vgwXmI1vQDmlia9tzaZSuIAlj7OKcAwqD3DTspQfXe4MBlFc9rcb2cvbCrHDWAAkvv3HhtqiVh+KbZPFA2gg0GHK7ouLdTm7d7E5MWL6yiVJ+IjNsUF+C2du15JtAjTrbpEZHRuc8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775152726; c=relaxed/simple; bh=lBe4YpWJXS/sZuCCHV9WDdwH1hkqW/YGfCjB92X6oqU=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=lyOxJ3ZjXJLtDuztobrqlEJ1b8BSPixzMQBAe1cUroonxxQG0rV4QY7RPqCvDRnbbcl4X9HYQzD8hAkrDgkivJTCwOKZoaX59xK+6r6Ox7CCImcicMxDOmH9vf0lY5b/uYibglj+AnW85y+M87sTRX+anFTcFMXQvqKFA9Uy+DM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=R4h/nqxa; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="R4h/nqxa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6EC3FC116C6; Thu, 2 Apr 2026 17:58:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1775152726; bh=lBe4YpWJXS/sZuCCHV9WDdwH1hkqW/YGfCjB92X6oqU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=R4h/nqxaaI/JOKP3X4Gup1XYtC4T102FTQ5qvlMyhJMFI2zcsFyJOQqK+5ypy3OxA t0+enSjocY6eB8mI7c/6M+OaAOyCtUZVgZG58iuZem7ndSW7hsam2rKbhloXK/dvAP 1i1qMZidrX4COpdZQJ0mR6kkF0H1FmaGFhzfU1hU= Date: Thu, 2 Apr 2026 10:58:45 -0700 From: Andrew Morton To: Pratyush Yadav Cc: Chenghao Duan , pasha.tatashin@soleen.com, rppt@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, jianghaoran@kylinos.cn Subject: Re: [PATCH v3 7/7] mm/memfd_luo: fix integer overflow in memfd_luo_preserve_folios Message-Id: <20260402105845.f4d375734c0b21a1203fb9c0@linux-foundation.org> In-Reply-To: <2vxzv7e9ftwd.fsf@kernel.org> References: <20260326084727.118437-1-duanchenghao@kylinos.cn> <20260326084727.118437-8-duanchenghao@kylinos.cn> <2vxzv7e9ftwd.fsf@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 02 Apr 2026 12:06:58 +0000 Pratyush Yadav wrote: > On Thu, Mar 26 2026, Chenghao Duan wrote: > > > In memfd_luo_preserve_folios(), two variables had types that could cause > > silent data loss with large files: > > > > 1. 'size' was declared as 'long', truncating the 64-bit result of > > i_size_read(). On 32-bit systems a 4GB file would be truncated to 0, > > causing the function to return early and discard all data. > > As Pasha said, KHO and LUO are not expected to run on 32-bit systems. > Plus, since i_size_read() returns loff_t, why use u64 when you can just > match the type and just use loff_t (which on 64-bit is long anyway)? I > don't get why u64 is any better than long or loff_t. > > > > > 2. 'max_folios' was declared as 'unsigned int', causing overflow for > > sparse files larger than 4TB. For example, a 16TB+4KB file would > > calculate 0x100000001 folios but truncate to 1 when assigned to > > max_folios, causing memfd_pin_folios() to pin only the first folio. > > Using unsigned int was intentional. We pass max_folios to > memfd_pin_folios(), which expects an unsigned int. So this change is > pointless unless you go and update memfd_pin_folios() too. > > I think making memfd_pin_folios() use unsigned long for max_folios makes > a lot of sense, so can you please go update that first before making > this change? And when you do, please match the type of the argument to > the type you use here instead of using u64. This can be a separate, > independent patch series. Thanks. I'll drop this patch. The preceding six patches are looking well-reviewed and ready to go? Chenghao, please prepare any update for this patch against the preceding six. Or against tomorrow's mm-unstable or mm-new or linux-next.