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=1794048875; b=l/u2eNkcM7QWuAt/079N/iQAARzGSsai+IdXeWO4DxHcVBmcLMdeVZInAc1bPDVhoYj+ LL0yaSX0UnsgdSnqHyGq3Hm+NHi9M1LPURmnnZ6qnszD5wBvY7ly6WE4Uak2u7Nhdvvvb 4RuyNylgGTuAUF5rw4AO4q74uz4jol2RZnmSyHl+zbweZ+Gmyrol27KxztGMwGH7q+zIM KvZightwREB8pi69+QNPggjsoqq24kMy2WVWNxy/b020J/EYcQO9vAXfWS9sACJJbj6eP nifLo2fMG3XA5VyPJaZX7IAjCdH+WYwrYwul3D4dl7P8cryJzUduNzNgz9zZKKZj22Q== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794048875; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=OfyReqbyyxiiLsp/o+mz7CLMT7XGFUETbpGTQDjx8lc=; b=nOz96vSOE9n1QkThGpJagd3o/SI1auz/LKDxHf7awPZE18bP66a2bxARGx3xmd8HxTJ/ fBh4gLAOCtO/rx4oUeRoHLSoV8PU9Kc+1CiCMsYzxgJDeen3oUE9Hyxob/gVHkGx5dBfh z1o/Nj3IoVQXLYCnKT0gNLucTj6j2gmsmXSkOJKgbLuZGz1jJfs8TCYRVA0r9jcsutV88 VuWme6PgI9UaIK2QTf0Ccjdn5F2UaqFWfDAQj3v2Ec46Hid9hYZ4v+VFUPHX5QuOMQmpr igYk/mQ3AaNU5R+Zq4AOoMF1RnLOepdTiHZ7MrjA5p6ia6Ovo9kj6P/ruKCeX9HjEDg== 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=neOndq9q; 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 9A5F1606A326 for ; Sat, 7 Nov 2026 10:54:35 +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=neOndq9q Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1A0DB1F0089F; Sat, 7 Nov 2026 10:54:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794048875; bh=OfyReqbyyxiiLsp/o+mz7CLMT7XGFUETbpGTQDjx8lc=; h=From:To:Cc:Subject:Date; b=neOndq9qvu1cX2Qys8NxX4O8XXZx3EOOoM8qhOz9U+dZEg3aY6nUbH/jNmljTY2EM UDFHPVsxpUBCRKWIux7oABAFLghhB0M0ODtbAkQiw/zoFhDpI6lGxDLx6dOHula2J8 cnoNVvmsOA3XZkiUhSiUPhFaZFnCVyVpmUZ/A96gAgHisZdPPf/o4/7sx8jsrzTrpj Qt44ai+Er1O58FG8UeT4GImQVNpboRYkaCz/Zxvk4fjYAvBj0Q08C9v2MFl917lQru z2CuVEiXQMmzJUVtY8bXnNxRs6AWibNxZk3FBDCAEiEDWK645jIARZsWPsq5q4Pwwc 5x5daD1X+/fkw== From: Sasha Levin To: david@kernel.org, akpm@linux-foundation.org, ngocthang2710.1999@gmail.com, ljs@kernel.org, rppt@kernel.org, lance.yang@linux.dev, liam@infradead.org, vbabka@kernel.org, surenb@google.com, mhocko@suse.com, benh@kernel.crashing.org, a.p.zijlstra@chello.nl, riel@redhat.com Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] mm: disallow ioremap'ing ordinary RAM in generic_access_phys()" failed to apply to 6.1-stable tree Date: Sat, 7 Nov 2026 05:54:32 -0500 Message-ID: <20261107055432-failed-6.1-4590752e20aa@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 6.1-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-6.1.y git checkout FETCH_HEAD git cherry-pick -x 4590752e20aa393cc0d4fe538c0747d14a98c97a # git commit -s git send-email --to '' --in-reply-to '20261107055432-failed-6.1-4590752e20aa@kernel.org' --subject-prefix 'PATCH 6.1.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 4590752e20aa393cc0d4fe538c0747d14a98c97a Mon Sep 17 00:00:00 2001 From: "David Hildenbrand (Arm)" Date: Tue, 13 Oct 2026 13:41:24 +0200 Subject: [PATCH] mm: disallow ioremap'ing ordinary RAM in generic_access_phys() generic_access_phys() can end up getting called on CoW PFNMAP mappings, resulting in it trying to ioremap anonymous folios, which especially the x86 code doesn't enjoy, and which is in general just odd/wrong. E.g., with a CoW mapping of a PCI BAR: ioremap on RAM at 0x0000000045623000 - 0x0000000045623fff WARNING: arch/x86/mm/ioremap.c:216 at __ioremap_caller.isra.0+0x4c2/0x5f0 Call Trace: generic_access_phys+0x130/0x4d0 mm/memory.c:7178 kernfs_vma_access+0x1ce/0x280 fs/kernfs/file.c:437 __access_remote_vm+0x58f/0x890 mm/memory.c:7256 mem_rw+0x2a1/0x670 fs/proc/base.c:912 But more generically, we should disallow access to anything that looks like ordinary RAM in the system: including allocating memory (e.g., alloc_pages) and mapping them in a VM_PFNMAP. For pages with an online memmap, allow only pages marked as reserved (PageReserved). This also includes memblock allocations, however, distinguishing them from other MMIO is tricky, and nobody should really be mapping them in a PFNMAP (except someone abusing /dev/mem, which we do not care about). So only allow access if there is no online memmap, or if the pages are marked reserved. Reject other pages with -EINVAL. Note that, just like other pfn_to_online_page() users, we won't care about concurrent memory offlining; mapping memory that can concurrently get offlined is highly dubious. Link: https://lore.kernel.org/20261013-generic_access_phys-v1-1-b3963ef76e37@kernel.org Fixes: 28b2ee20c7cb ("access_process_vm device memory infrastructure") Signed-off-by: David Hildenbrand (Arm) Signed-off-by: Andrew Morton Reported-by: Closes: https://syzkaller.appspot.com/bug?extid=49b1021becba70c1f3f6 Reported-by: Nguyen Ngoc Thang Closes: https://lore.kernel.org/r/20261001152524.171115-1-ngocthang2710.1999@gmail.com/ Reviewed-by: Lorenzo Stoakes (ARM) Acked-by: Mike Rapoport (Microsoft) Tested-by: Lance Yang Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Suren Baghdasaryan Cc: Michal Hocko Cc: Benjamin Herrenschmidt Cc: Peter Zijlstra Cc: Rik van Riel Cc: --- mm/memory.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/mm/memory.c b/mm/memory.c index ed64455c73bdb..34e60a5baf7ce 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -7129,6 +7129,7 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, resource_size_t phys_addr; pgprot_t prot = __pgprot(0); void __iomem *maddr; + struct page *page; int offset = offset_in_page(addr); int ret = -EINVAL; bool writable; @@ -7143,6 +7144,19 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, retry: if (follow_pfnmap_start(&args)) return -EINVAL; + + /* + * Reject anything that looks like ordinary RAM, including anonymous + * folios in CoW mappings or allocated kernel memory. Note that we + * cannot distinguish memblock allocations from non-RAM reliably, so + * we cannot easily reject them here. + */ + page = pfn_to_online_page(args.pfn); + if (page && !PageReserved(page)) { + follow_pfnmap_end(&args); + return -EINVAL; + } + prot = args.pgprot; phys_addr = (resource_size_t)args.pfn << PAGE_SHIFT; writable = args.writable; -- 2.53.0