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=1794049402; b=ZocFkZUJbClIdpv4lLiDBYo7xY2DdnBX7cf36nbnnoieRuRl5NMmXWCmQ8//IGhg9fDF 28GhVUwYLRoqb2nhrAHLfQBVbzRUdowc2VibE+tHVuhb6XxPkRpu3oRYgIy1x0qvVjKVs hz80hUrVQkYplNMj8vzaO/4cxeJYx6/N1GK/o3Cpz7V1IwyVPuIGNS1C4JBFDxD2h5+Bj iE0qQzzbjdL0YGAJRqS55L09hadbwZCkVkDC7+Fp6fSA3zA7Hj1a1X8mNY23wMflgOB00 LjeTapWk+bZtGFSR5dIlBX/5WiiHM4w24VH+8zjQwF5zn7Q/XxWR436UaoLUBT/db+Q== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794049402; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=Bu8kNuOvhDJhtXC1HumyJFWHQYGicz5WFbvrchgm3lo=; b=H/WAcObJ7OFE9GngY+jtiVtG2LvNhyBJoOPOHTk1L4iy55Ul3t72A6aU017iX35PAztr VK5BnGFzK0NSFCYen4Msgg3ChHvebPtf8kOaId1blJAodtbRQPA/E6W57k6xZ4kk3ZtA8 YUbuSGNTzJmYt3GhxOllx9Iy8FEZUZWI06mLFZcblDRwI9ros2xJt7KYQIROGaWWqWpTA e0YWGHQNx4Feh5+0X/zZsdTWZ+RLK2psg4AeW2ItsLt7QFWEDBLJRtFNIKkJArRowN9CQ nBp2rL8FWdMXyVj3ih20W0W+BJhKKDl1GrE6N0cvhbiaGI6Bq6VIhKAij91Qhe6vbyQ== 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=IcoKwKWM; 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 7918F606A326 for ; Sat, 7 Nov 2026 11:03:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=IcoKwKWM Received: by smtp.kernel.org (Postfix) with ESMTPSA id 096C81F0089F; Sat, 7 Nov 2026 11:03:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794049402; bh=Bu8kNuOvhDJhtXC1HumyJFWHQYGicz5WFbvrchgm3lo=; h=From:To:Cc:Subject:Date; b=IcoKwKWMg74gxaphjfMES4acWTepzr2+pH8Lz3/2nGB8mGvMZFKMWEz/qE5VHAIWz srQBrgtBLrVYcyRtWZ8n9I5m6qYThCtfpv0xJasoEHTKHb2c3YJDcBY8I5CtAIFuEm zv8mLcbVr1GoOvrJtSP/YfXAJn0STekyeSa0Be5K7bgtJ/RveXlI1KHfr0RoQWxspr UwVL5ZZRkn2A4EveRmCQ8zgMW8po0OaOlj2gz5TZbHOTu4fy15LAJ8RuG87/6yDBSK PyOmLAN8huL35nH5M2V8X0hcfoGRg5rjpq8XQgB7S6/iKBdM2aaZITCBU16z1HmeXO 6+fjGeQ2fPP3A== From: Sasha Levin To: rakukuip@gmail.com, weir@nebusec.ai, akpm@linux-foundation.org, vega@nebusec.ai, david@kernel.org, notasas@gmail.com, liam@infradead.org, ljs@kernel.org, mhocko@suse.com, rppt@kernel.org, surenb@google.com, vbabka@kernel.org Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] mm/memory: constrain generic_access_phys() to page boundary" failed to apply to 5.15-stable tree Date: Sat, 7 Nov 2026 06:03:19 -0500 Message-ID: <20261107060319-failed-5.15-ae0298a5fbef@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@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: 8bit The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x ae0298a5fbeff32951c0d31398ccec97ec6aa0ea # git commit -s git send-email --to '' --in-reply-to '20261107060319-failed-5.15-ae0298a5fbef@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From ae0298a5fbeff32951c0d31398ccec97ec6aa0ea Mon Sep 17 00:00:00 2001 From: Luxiao Xu Date: Thu, 10 Sep 2026 11:42:50 +0800 Subject: [PATCH] mm/memory: constrain generic_access_phys() to page boundary This patch addresses an issue in generic_access_phys() where accessing memory across page boundaries in PFNMAP VMAs assumes physical pages are contiguous, which can lead to accessing unintended physical memory or exceeding VMA boundaries. generic_access_phys() improperly validates the memory access range: it only validates the start address using follow_pfnmap_start() and passes PAGE_ALIGN(len + offset) to ioremap_prot(). This poses two problems: 1. In PFNMAP VMAs, consecutive virtual pages are not guaranteed to be physically contiguous, and individual PTEs may have different access permissions or writability. 2. The mapping may cross VMA boundaries if len extends beyond vma->vm_end. Constrain the access in generic_access_phys() to at most the current page boundary (PAGE_SIZE - offset) and map only a single PAGE_SIZE via ioremap_prot(). Since the caller __access_remote_vm() already loops over the requested length and handles partial transfers, it will naturally iterate over the remaining pages. Also add a missing (resource_size_t) cast during PFN re-validation to avoid truncation on 32-bit PAE systems. Link: https://lore.kernel.org/e06e28a46c2a176238f03b5740df0913e57c2861.1788842306.git.rakukuip@gmail.com Fixes: 9cb12d7b4cca ("mm/memory.c: actually remap enough memory") Signed-off-by: Luxiao Xu Signed-off-by: Ren Wei Signed-off-by: Andrew Morton Reported-by: Vega Suggested-by: David Hildenbrand Acked-by: David Hildenbrand (Arm) Assisted-by: LLM Cc: Grazvydas Ignotas Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: --- mm/memory.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index ec63dd6212ac5..926276d419202 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -7131,6 +7131,12 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, bool writable; struct follow_pfnmap_args args = { .vma = vma, .address = addr }; + /* + * Limit access to one page at a time, as that's what follow_pfnmap_start() + * guarantees; expect the caller to retry to read larger ranges. + */ + len = min_t(int, len, PAGE_SIZE - offset); + retry: if (follow_pfnmap_start(&args)) return -EINVAL; @@ -7142,7 +7148,7 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, if ((write & FOLL_WRITE) && !writable) return -EINVAL; - maddr = ioremap_prot(phys_addr, PAGE_ALIGN(len + offset), prot); + maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot); if (!maddr) return -ENOMEM; @@ -7150,7 +7156,7 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, goto out_unmap; if ((pgprot_val(prot) != pgprot_val(args.pgprot)) || - (phys_addr != (args.pfn << PAGE_SHIFT)) || + (phys_addr != ((resource_size_t)args.pfn << PAGE_SHIFT)) || (writable != args.writable)) { follow_pfnmap_end(&args); iounmap(maddr); -- 2.53.0