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 59CEF606A31B for ; Tue, 27 Oct 2026 09:37:55 +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=O5o/J06T; 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 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=+rNSdhvOTHmuEN3Ml/bfsrTqF8UwvJdcqDi4DNQ6sTg=; b=O5o/J06TZlSPQ/TwnR5f0sf9qc GyBTkJ1lWRmnzMiguNFwMoCT5xEOfW6xxK7I9EJCV7ERiDXdAy4mNs3ZB7ruZ9wEyEBbjfw/B/KbJ I73dqlrRPU1uAc7XocJXT589pnDWHZyYxivtwSyJ0L4qkd7PAeiZpVLwct/K8PcK7sJO8tz4vB6/v 2f962l8vWhPm3zAbowHPNAdnPIuqcUcWRSRbGBE6dHTFhdNZsQR+s2foPDgkvB43MR0mIRDMKGsYH Tc+LN99cJKcGABoE6aT2Uyeef80LuUgZ8aqy7LP1+pXweppS7FXNEMV7Wl/w048DnSntS7jkUaEUo iaBiwYvA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLdcw-00000004BSy-42e4; Tue, 27 Oct 2026 09:37:54 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLdcv-00000004BSj-04on for kexec@lists.infradead.org; Tue, 27 Oct 2026 09:37:53 +0000 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-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 12:17:41AM +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