From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D3892606A31B for ; Tue, 27 Oct 2026 09:37:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=U7+fBT3l Received: by kanga.kvack.org (Postfix) id D6FA46B065D; Tue, 27 Oct 2026 05:37:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D46B26B065F; Tue, 27 Oct 2026 05:37:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C84B16B0660; Tue, 27 Oct 2026 05:37:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id A65E46B065D for ; Tue, 27 Oct 2026 05:37:55 -0400 (EDT) Received: from smtpin10.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 310CFA09C7 for ; Tue, 27 Oct 2026 09:37:55 +0000 (UTC) X-FDA: 85367904510.10.5E7621C Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf29.hostedemail.com (Postfix) with ESMTP id 835EE120008 for ; Tue, 27 Oct 2026 09:37:53 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=U7+fBT3l; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf29.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793093873; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=+rNSdhvOTHmuEN3Ml/bfsrTqF8UwvJdcqDi4DNQ6sTg=; b=2q6neOJqfxjMmLGLQNtOFqLzOw9yl678rKHjg7tHp5iqYcvId/pIQe0Ri9Lj2LtB6ULwL+ EuMNw9mtxc1F5n5mkgSq280DWL2MD5zBHn350rDpv7IQyrzHS7WbdDqyZ4kWhNam7mIbl1 RGDj8pVKo6onH7esyW6CcaLpbJhAsR4= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=U7+fBT3l; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf29.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793093873; b=pSBTT31csei/Nj1rceVPV7hLF3jUiIV/KERe8XbHc1VseI3cqMh7IoUXtAqAsAPE9bhcLH lwn9L/HDnl6TMZeDQSOBhQRSSmjVdLUYhZbhWc5rFRGud1O47HXuN9xNKoDUbDvost8K6s c6G+uKpbCLyXCj1C94/4TfQ4HPwKF6w= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 6CCF042CE9; Tue, 27 Oct 2026 09:37:52 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 490C11F01825; Tue, 27 Oct 2026 09:37:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793093872; bh=+rNSdhvOTHmuEN3Ml/bfsrTqF8UwvJdcqDi4DNQ6sTg=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=U7+fBT3lehpQpFc3uJKZHtVpRgi1GtGHT6z3b8kE2S6FeF6bFDBDYsG/DhyOz1wlU gkZvgV/b8GwC5hBF2vuMNqTpih+mBOGm/magVJ+5tlmYMUc8rC0HgDbxkq4C2ZdX7/ ykFSl8AC+Hlev3LyWJ5Ey8IgtYvUDz6NSxnqxhKKoOE4gmRJYKRD4ktRxpkFHa/N0B GZx6g/C9Es4dpnIsGGa84PHZ4w1B6j/LHsH9niHHf9ry4zHK8ev9PN5ziVl0zIXEG7 p4yl/pvZrQHfp2KrQDErkAMPWJNescqIgRyziMHz4MrRviwMpP912C23Dpz/85S7eu i5GpXe5pXwalg== Date: Tue, 27 Oct 2026 09:37:34 +0000 From: "Lorenzo Stoakes (ARM)" To: "David Hildenbrand (Arm)" Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, Chris Mason , stable@vger.kernel.org Subject: Re: [PATCH 21/46] mm/gup: fix out-of-bounds write for nr_pages == 0 in GUP-fast Message-ID: References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-21-6f74bec9a5bb@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261027-fixes_core-v1-21-6f74bec9a5bb@kernel.org> X-Rspamd-Queue-Id: 835EE120008 X-Stat-Signature: e4u7tqx8p3ebj59su7pchztwaru45udq X-Rspamd-Server: rspam04 X-Spam-Status: No, score=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=unavailable autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793093873-464671 X-HE-Meta: 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 BpBSi8gQ fVb2Zw0SRNaoCNoF7ZuxtSlLXlOpbRTxLMX0XJqezJbbBgsJLtZUPQz0wYl3b0WwIZvavyFFNmGBbJyqdhqOsupb25uXIwVUv/FbhhaaqOnvdXXpETwWIhsJ9cVlwA7xeo3AzbhmX+6gK+WWZsvMB36raSijYIGDF9jIXNiObG9jh7Px9EYV+76moLN6XsXH074qwv4gqDXkVmLOl8DZDCJRYNWnIeSwKeWraqLnd53VayJcBEUJTXJsxlUKJZlXka7xdJ2ZOo/ifTjbg9msTYUoauVX3PQ8twAo4NKpGnqURmAJ9/oyj23KkhNR3erVfao2PKUhlTCTd+cN2rQIBJNaDrRbpLhw3Mg3XKalNfzGt0JWMnTtlc9yNnm2A3VU6K6HYn2H9X0BTocXA56KO1RU6IqDYrlJh+FZ9Z8cLaZGBPHcPLxgpKxgoNg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Tue, Oct 27, 2026 at 12:17:41AM +0100, David Hildenbrand (Arm) wrote: > From: Chris Mason > > With nr_pages == 0, GUP-fast still enters its page table walk and can > write past the caller's page array. The old end <= start check caught > empty ranges, but was replaced with an overflow check. > > Users such as OrangeFS can pass a zero page count derived from a > userspace-supplied length. So let's return zero for nr_pages == 0 before > starting the walk, just like GUP-slow. > > Fix generated by an LLM and sent by Chris Mason in private. > > Fixes: c28b1fc70390 ("mm/gup: reorganize internal_get_user_pages_fast()") > Cc: stable@vger.kernel.org > Signed-off-by: Chris Mason > [ david: simplify description ] > Signed-off-by: David Hildenbrand (Arm) LGTM so: Reviewed-by: Lorenzo Stoakes (ARM) > --- > mm/gup.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/gup.c b/mm/gup.c > index 47e7ae152cdf1..9906965893431 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -3204,6 +3204,9 @@ static int gup_fast_fallback(unsigned long start, unsigned long nr_pages, > FOLL_PCI_P2PDMA | FOLL_HONOR_NUMA_FAULT))) > return -EINVAL; > > + if (unlikely(!nr_pages)) > + return 0; > + > if (gup_flags & FOLL_PIN) > mm_set_has_pinned_flag(current->mm); > > > -- > 2.43.0 > -- Cheers, Lorenzo