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=1794047935; b=JZ5Bm3QEU7ExWBqne3MZbWkUrol1A9T90jMPply+nBW3vp/NPZGiVEKPtFbDPJF2v0TR 7M5oDLmdG3QGwTS0uQM0//sbamhgaIhcjHmiFzHOWQlv8dYkf4Jn1GgxdxyQQIAyHDvp9 Rt0rJalfio+TY/NJGhW389m3FDzNGwjeykwL2CT7xIO3pYkT0KU32Ez8hrbOOB3I0YCod 6oZnr7c/hvs29VdFRPwarY/sZkdsitZTH3iSMaYQ6vmW+tSpvvMrHyoTCoLNCuJIAfWlk EujIDqOcdQAVG1YNkWgA1th2eQO3Qr5AxeAh6OymvfCjWXB/j5VfLgcsKzOwWY3TEvg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794047935; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=cW7CTU9iwqDp/tbqv8BUl7Jjy5+kMomtuX8EjXzQchk=; b=sxaFs7gmZgTxavLB5Pa/7+yLRoX4U5kRBz77y97tjHIycBNer4/oMu6txVM05YZAf+eh Bx0h0H4F702Lm0gPCMzmVDw86kOA7SurNzDL7WHIIm8PfBlLkLopGCZ/oiCa66D0riXwN keS/lP5VNqyBy39Q66K6QHlmnXQ8aPZKXl4+QiiGhHqMxC6+5iWio7zQd3x0TrgCeA/gw ZNE7/APKOuITrih7N3r6u+3JdjLQAy/d2p+qBfD0W6eyAxehFJkNn5WXESigJ3J6qdMYr utyRd9bQdaWELZqk49eUQp1bA2pcbTUpZj2uzuezPDXt8hligoVkAnqMzCcqYaK0/8w== 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=EB1Q46BT; 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 5428C606A326 for ; Sat, 7 Nov 2026 10:38:55 +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=EB1Q46BT Received: by smtp.kernel.org (Postfix) with ESMTPSA id C31611F0089F; Sat, 7 Nov 2026 10:38:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794047935; bh=cW7CTU9iwqDp/tbqv8BUl7Jjy5+kMomtuX8EjXzQchk=; h=From:To:Cc:Subject:Date; b=EB1Q46BT+T1KdCC5vbabqN4ltC/6A+0BbPmgvyTdSNlSKVbRgNX3LiHROVE+Vdin1 fo9gK1I3zPZXqqPCzm0Gkxeav99FT0xIj6vTTH4+6j93ewFQOgc/snWqj54oRWuGKT SjlDtwXbmHqkR3dQtadKqYgZ4qE5nhcfYRP+LXNhXrE3p61JqL/X4fkRXLU/JOsjeq oHow9A277pUT7+LjK4RWGV3eajUGikuO6wsfE0igDz9IU5/2xcKwGCj5EKdQ1JfAmO OzrCkRMS8amYmiOQFENGmwin5OSWrYP4xLBZFkkuk46idUslYGLbpUmgatF9/MkKS4 jTRNY7J5PEv5g== 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 6.6-stable tree Date: Sat, 7 Nov 2026 05:38:52 -0500 Message-ID: <20261107053852-failed-6.6-4590752e20aa@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 6.6-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-6.6.y git checkout FETCH_HEAD git cherry-pick -x 4590752e20aa393cc0d4fe538c0747d14a98c97a # git commit -s git send-email --to '' --in-reply-to '20261107053852-failed-6.6-4590752e20aa@kernel.org' --subject-prefix 'PATCH 6.6.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