From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E786F606A31D for ; Tue, 27 Oct 2026 09:35:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=0sgZXX0/; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Z3V2ir1f DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Unsubscribe-Post:List-Owner; bh=GyDf/T3A99e/UK5Tx0KKev7xPaxEfXMruyrCYj6de1U=; b=0sgZXX0/lWq84BytmHeYjLLH+e vSDg+sSo3y1Ws+mc5A/DVTLKbl8VAptozCKkEy8s3QPIIpMNe0BHNa0XESWvnbis254GOrhauPrWV Dr+kYKrGkE0l0E5dw2iWYXhEsJBJBiGbwIHURGlBAfdiW/JYoi3dJfuqLP+g+uOy6dAg216Ns0rVK KhpG80N/XaasWsc8QnRTWo3HgAMxw4Cq5XteI9peoM7pb9ShVTvqH/9/jfj1J6qtHYrPNncNbNKWZ FmZHyCtXdc8vZM4RsfBBwmL5wHB8lIoAuZlk57ZHaF/WnMlK3WFwrFh9DKoldsf0YcUivk3FlurXx VuQwI41A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLdaO-00000004Alq-2emi; Tue, 27 Oct 2026 09:35:16 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLdaN-00000004AlP-2IqL for kexec@lists.infradead.org; Tue, 27 Oct 2026 09:35:15 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 2E4E460052; Tue, 27 Oct 2026 09:35:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4CD641F01825; Tue, 27 Oct 2026 09:35:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793093713; bh=GyDf/T3A99e/UK5Tx0KKev7xPaxEfXMruyrCYj6de1U=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Z3V2ir1fhLjLEOG38tPqPyKd7K/FHGfPC09OfR7eOlE/pdqk+8s3kVa1i4DQbH+Qx MZ32NLc7julvf25Egjxt2K1dVEewhL3Of9L8IHSEkMikSMuPsfkdtPqT3BAFRQIx4l I2aocqwSNzVOB8HXoD0iEYYGXcOv8ZXfRuVth/j1TS6G/Q38VWONKl+4C7n5MEPxNA MdDQY8Y20j6O/Wno2AqROjn/Br7ZnF59rm1EwFzdyTg2TjL0F8dx2lgZTIglHC5tyA DHYvTnMV0DHzDPWwpSElNE8EW4/oPBEyMA8Gm39jeV4/zgUOyB58UgoLt0XQBoz9Do 0CxG7SV58ggfg== Date: Tue, 27 Oct 2026 09:34:57 +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, stable@vger.kernel.org Subject: Re: [PATCH 22/46] mm/gup: check for overflow when converting nr_pages to bytes in GUP-fast Message-ID: References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-22-6f74bec9a5bb@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-v1-22-6f74bec9a5bb@kernel.org> X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" X-Spam-Status: No, score=-16.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 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 12:17:42AM +0100, David Hildenbrand (Arm) wrote: > The overflow check in gup_fast_fallback() only covers the addition to > start. The preceding nr_pages << PAGE_SHIFT can already have truncated > the length on 32bit. Insert rant about 32-bit kernels here :) > > Users such as RapidIO's rio_dma_transfer() can derive such page counts > from a 64-bit userspace length. > > Let's just check_shl_overflow() to reject any such overflow with > -EOVERFLOW early. > > Fixes: c28b1fc70390 ("mm/gup: reorganize internal_get_user_pages_fast()") > Cc: stable@vger.kernel.org > Signed-off-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes (ARM) > --- > mm/gup.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index 9906965893431..48e1bfe5ab9a9 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -3214,8 +3214,8 @@ static int gup_fast_fallback(unsigned long start, unsigned long nr_pages, > might_lock_read(¤t->mm->mmap_lock); > > start = untagged_addr(start) & PAGE_MASK; > - len = nr_pages << PAGE_SHIFT; > - if (check_add_overflow(start, len, &end)) > + if (check_shl_overflow(nr_pages, PAGE_SHIFT, &len) || > + check_add_overflow(start, len, &end)) > return -EOVERFLOW; > if (end > TASK_SIZE_MAX) > return -EFAULT; > > -- > 2.43.0 > -- Cheers, Lorenzo