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=1793439943; b=5lW+PiW5k3XUmRsNQ7ytYqyGuJYMiymkvk9sbAhYCuWoZSYDvtce8Guq7hov9hqdoERV Mm1/2x4Wyw7WSr7HGtiHbOWhTfi/yKvQngXfzvP6ggfHU9aIJ0BqGpYDbZWMKLSu5N3KO iO9zFoo1A3Qw5LhtzHPpPd1vsjDYXSzxUQW9iRYxPQqZfBs6AiWCIoTvkCHYt9ECDqCHS hYxqBKzb1wMNjo985UkwqYQl3200jJgDY10Tvt/ZjVF3NcqINXPDTvolc8GtffUOD14b8 1bibjAVIgLVh38ErD9fMs5MxaQNgi29yIV75fBAp1lK7TAiZzNnN5q2v3mzdtvy/DyQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793439943; 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=foIE8/qjRxOslIMIVm5LWTcoDseO7kpGoD14hc0ILxg=; b=m0ryLl9ef99p4riUWw918zFO1JtX/TxIowu2LKgpNChvN2aqNaYU3iy1ZZW1cqgL4JHZ vY8DPqQI1F4fv5vQi6ftnDDyBsLa37zJ7SyoKAqbCoXdx+/VibNH4648EUn44j2gHMJ3w YGgJvQTP9Lln0OWthDjDy40sPrAKmhPoSiMuS237acZwq9BCt+hyQxmeDkmu4+dvj6wvE jwV3Z3iOHEVoLa6ceo1Jyh3Uyb7pCbffpQM9dFYIHJbv2RZkYKaEbYdYYaCgPxBojGoMv YICe9mb4pdSuJs7n+M+AdUR9wggu8TQ+LqXD0hkdqZwlG+2MIJTr2LbtbecMgD8cIYw== 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=JhV9oGMq; 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 CA50B606A31A; Sat, 31 Oct 2026 09:45:42 +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=JhV9oGMq Received: by smtp.kernel.org (Postfix) with ESMTPSA id D56871F000C1; Sat, 31 Oct 2026 09:45:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793439942; bh=foIE8/qjRxOslIMIVm5LWTcoDseO7kpGoD14hc0ILxg=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=JhV9oGMqjIuZGgcbHEUsRikcUmJNTkInVxMbDD2McBF1KHRCOovytr11YurFRKmY+ bzpFUCXJV07KGchANo9OXAYly2i+TAjzzG2qyAyH0zYRfED/AUnwLW/4JR6ep8DOEp 3ob8fsc2zXmkJajPfwx9ACN5aMF4fl4RqsnmBccaStiOm1Ik3W84FuIM9kDgSEnVcs FnUcTU/F9+4T7XCWF7hfPk1mhEKqJzRhHlBbv4kVrzqvgm/NnX6C0xi3dX2J6sa5iR Ryhd7cB6JyGhcESjQmqHd0GH2cyaVRdT7FizFV9PWwZW6Rt8Hkhe6GmVGYIIMTUxku 0gFPxVWBEFA7Q== From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:39:50 +0100 Subject: [PATCH v3 21/47] mm/gup: fix out-of-bounds write for nr_pages == 0 in GUP-fast X-Mailing-List: linux-fsdevel@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: <20261031-fixes_core-v3-21-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> In-Reply-To: <20261031-fixes_core-v3-0-d6437171ecc3@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, Muhammad Usama Anjum , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1320; i=david@kernel.org; h=from:subject:message-id; bh=R62eMdMsJypxqcni0WbltJmOI5kqokR7T4ahYSHS7oQ=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLKebk9XufzzUt3qVRK79jW/zlzmvMenZ80MsUTHtrnHE 7tlXOZqdpSyMIhxMMiKKbIEBd83ePlyXW21Gx8zzBxWJpAhDFycAjCRtAqGv6InnopkrO0IDNHq 7pC+cvvWiW0b+d98XM7UJ9iq53RHYQ3Df69HC3Z+ryqu27DmAne4j/fJiz8+bFvAecZ3t5uDiFP eOk4A 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 Tested-by: Muhammad Usama Anjum 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 cc4fa18783ce0..1c2ac7c66c309 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