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=1793057071; b=TSQArgxWqWwXYzJbzCj0L2oh7AZojNLRgX5Xl55qzOHrEvJVA9cVTMD3agRh0SBsuWKY 8wI60xhELk6aTyStWpbXX6WQ+InbHPgjmzl49MRm1H525/4VPARCzwHWOkNN8g6TvH70i ofyzKIFK5U1bg7Pu4ktHo8MwNmgdqJINeUO0FbqOOmqg/2TxPNebS6p3JtlODYzW55SdF o8CfyL/iXD/aBkZMoE3VaGu7lXxGXriyD2gVSMYBkLBLx1u9QvANje2vrFu5pIw4UXG78 CEHLpS0WikIUsXudRx5vDNzS5SoUO3hefluLyehLg2d/cmbK2Mvoxrj3ajLMsVyJfOA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793057071; 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=MUiVnQIcW4HK+Vvqa5OhN89hQ5i9YryKSTF3EOLnRhs=; b=MHuyKuFr38rOYXKIkzmfCubOjo1LJm3j0CiyA9+WJpvCnG6EQQHhtBjgkWHErXhw7Iib p5ndCzUsySudMA2FXwWoKnVtvASCT6iLnQicCGCYNMm/fblbWophP4vQkEr16Ro/cBGJc LeupWOiSKh7Iz3a8wLs8TVSDtRapaQckwxhnRNW4xXHlN2VjFbqa8TJHJDI6nO61YTb9M VaFpSqGOfBR0UR4c4s3QsrJOA5g41JB9TFAmdxfTU0P96qgKlaeXtjs5YaC5ICzjIPp0d ATkrjjotNjTaLhvftzE1ZTLMcW8a5iTjv0Nj3r5mX6DOTAWNIXRFl2hkipNO9I7OW4A== 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=OzH8AW7I; 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 C928A606A31A; Mon, 26 Oct 2026 23:24:30 +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=OzH8AW7I Received: by smtp.kernel.org (Postfix) with ESMTPSA id 19DC01F01825; Mon, 26 Oct 2026 23:24:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793057070; bh=MUiVnQIcW4HK+Vvqa5OhN89hQ5i9YryKSTF3EOLnRhs=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=OzH8AW7IZVGSLh2s2JrXn3LgfDvl1ZX4yFb3GlfsKgz8zoruMSoZEux9/uq7Tk7sm cs4Oevuzm9hv19FFmzb4oVFDDyN8hTsXOa6ga9Wfsm5s0IDEHvgPHKHT1iRlEt6Wlx jX+TKAvX+UWsfR/O6g1EGXksf6/NAU5KAIgRyfAIxs3u0nD6husexzjL6i0H+JmNDj QvoT1xFpiuuavcAk/OvUsImVM/yKW2pqjZDDZvkv/sFj6K5bneJ1bUwoy5GawuHUzZ 931Cja01VhM36lJwgGvGp6aGe8/8ws02QJV+KXzzxA8UueMTlx/UmBS8gk/lw+F0G7 w2duGXjGqq0LQ== From: "David Hildenbrand (Arm)" Date: Tue, 27 Oct 2026 00:17:41 +0100 Subject: [PATCH 21/46] mm/gup: fix out-of-bounds write for nr_pages == 0 in GUP-fast X-Mailing-List: linux-kernel@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: <20261027-fixes_core-v1-21-6f74bec9a5bb@kernel.org> References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> In-Reply-To: <20261027-fixes_core-v1-0-6f74bec9a5bb@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=1165; i=david@kernel.org; h=from:subject:message-id; bh=+4EllZ1FmTDP2PkVD3jcp4reP8xmeyVcibo3mkhoq5k=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLLu358669na3pAFl6/pLlittcCkyfDvlTqOwCWbPfX87 u3WdpqU2VHKwiDGwSArpsgSFHzf4OXLdbXVbnzMMHNYmUCGMHBxCsBEohMZGW49v/1k3cwERfmt n7+fPaFx4sZu2c8NIUqvN6qeE//yxBuoYsd97QN6BzL9n+U45fx9aXrcwfOcrdWLPY5TbjzqWTN 3FwcA 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 ] 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 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