From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793306320; b=IMGMMqiZLHB96r37LbD3mKEJJmT1OB/MvY1+n1KdkYd6hWtjFGrPPNQIS/m9wTqCS0sb dN+xhGMDIZ33P25lfKOT2vL1cIOymeeYGE57CPX5qJ1ArFDd8IxyWdrCL/unwBM/UwRDz hxGxUaNCXBOKjOpJT17ALVR8d8DJcbS/3exFE9nd5FbWtwmgsvg/lC/4PDtv8xvNkjNSx fJi92P1g0pksOWpYYY0I7yP4N1C/5K2k1Zsp60IxfJlZuve+/glBVwsVuM8oHcfDg3FzE k7r2rVZAhTAKj0evyQZTtTRtV9o50t0Nm4FBGbpYFOIB8PTXwsZPjUjrsTtaz2fByqA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793306320; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:References:In-Reply-To:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=hUEcnN9ydaxDMlr7FSPNgc2BgiAcB7rSVu3xqMV261g=; b=l6ARUybesMpaOSQJTEo4FLVwG4Lp/xkacleZWxOeDnzlqgghh1+G3K8uWSflNRRsshnT cJoiIRg9WAzK9navgXfiM7MAdy7whUcxYTSoH4aEbHZoRAaN13J1IpZ35MS1EIc4T241P 3Aq40H1E7h0WfrBDV6JTxMzmQaXsA8gfoHG+dSoRot9Vc9JxsgCTNxP8w5QOAxEbHRITy FgocJpTXnUyreu+s80w9XXr68DN7n4wf6wrjjhDqHmOm5g0CbTobk+fVcACXmBoT2k5tn QLCrcHtpt0EUEw0j8UGAf4advpfinmStgE9wYYG5VlARWZKusTB6sSTX/ll3PNPllcA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=oVdw61b8; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6F81D606A320; Thu, 29 Oct 2026 20:38:40 +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=oVdw61b8 Received: by smtp.kernel.org (Postfix) with ESMTPSA id DCF331F01825; Thu, 29 Oct 2026 20:38:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793306320; bh=hUEcnN9ydaxDMlr7FSPNgc2BgiAcB7rSVu3xqMV261g=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=oVdw61b8fprlozgBHncc41LpdVLG5SLHt1W2WOHHdwpmEHY1UxuvvBPOvqfUxJ6TE ypj1G/DGtqCz4M/Mncb0zLIyJD7YZU5Q9CwKBWyL9J9dnBrvu/xczhapnmY6bqMauH cFW+yKoFtTCsaGgX0DaGpv7jF2hxRsfJnJ0YRpK3Cjo5KggitCplBM2+XWYS/AUOMh 5Qtft9UTttmKosFmaVLBtNXQus22sqElhihxeqFdjS/65EW05g7NDzHOAN3aITVvcf pDVlw7VhPB6Fkbvk3twLQO4Jx+uPVK41BSLLOJJbyUqRT/3NwuiE1YXtG+OOAUcs+j AEGV44bySO/jQ== From: "David Hildenbrand (Arm)" Date: Thu, 29 Oct 2026 21:33:16 +0100 Subject: [PATCH v2 21/47] mm/gup: fix out-of-bounds write for nr_pages == 0 in GUP-fast X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261029-fixes_core-v2-21-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> In-Reply-To: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> To: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , 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 Cc: 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, "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1263; i=david@kernel.org; h=from:subject:message-id; bh=nCaomD0R1GmRaMbC4ikA/oDPAe1RZtNKP6V5LWq8bsk=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLIer227ZSqbsjfo/PkOsbOhrnde/K8U2hdmLqwoELi84 uqRtBdJHaUsDGIcDLJiiixBwfcNXr5cV1vtxscMM4eVCWQIAxenAEzk8WlGhuutW1yb5HykeVbc c+eWPREaIBpb4SyWKbC8rZtNv2v1F0aGKVM/LJjuEBViqMyy/c3RD1erLQu2rvZ/6eWeIbAgyci XEwA= X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A 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 ] Reviewed-by: Lorenzo Stoakes (ARM) Acked-by: Muchun Song Signed-off-by: David Hildenbrand (Arm) --- mm/gup.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/gup.c b/mm/gup.c index cc4fa18783ce..1c2ac7c66c30 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -3215,6 +3215,9 @@ 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