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=1794329408; b=BvA/e7qQd3sNZnVpmyZA87VNTrQOG/NlYVI94uuwb9V/C7nJPwa3xq+4N7OWpoqvRVIP Rbl2DALI8e4O3BQxMLsck0rm7TEzVDuZCb6fDlEZ5u7udmHdijHllu8+Yy9uZ3nR+0lc6 dp0g636wH+cOyyFGcM0ngdMOG2gJVsztHS6K1QRYAdI1RKXk9NXpi+iY7gqJs4Qf14wdI FvdtYlJC+uvnbbgTuZlKbbdXG1g7R+cac3GRW5hPvTQQSeWJtYCznB0kIqBY0r56TW37m AewmFtXSSp0sY90PDh6Ck0QyIalXUQITHBlniXXQfJKkQa4BdQCiej4e0bjTfBfD6fA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794329408; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=pS0MHbEiTw9KXRiEpd5CeLRAl4oXVL8Oft6cJCAu4mg=; b=zeZqv+1JNTlNou56Y8zxtP+8LqfvC6WGuW3m0sNxaEGpZB7pNBzt3tKXLIPO6rJ+T9U0 Ph6/K4rgH8FoVcZVOlr+UYPPab2TDDQ4O/bMRTDemJQXXGLsXmHq3QEACQ2t3jQMBf/Se 5o/jUhiDllR4/YcjzaJw2ReM70gH2SvhJAPpvsHRydIA+mAr1/qke8wFo04C3BBwbHtyq 7DiP5rNd6unYkprBnbz2TM0FLwufRfS3dl+u8WO/jMynuSLCQu+j/NDBePWmuQbKF8Boo 1ww8XZBPvl0+xAp50L9EQcgT2/Xnk2Hny6vliEYCpdcUo8g5l9K28d2iwX71XdUBd+Q== 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=emdx7L4B; 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 2615B606A321 for ; Tue, 10 Nov 2026 16:50:07 +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=emdx7L4B Received: by smtp.kernel.org (Postfix) with ESMTPSA id 105741F0089F; Tue, 10 Nov 2026 16:50:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794329407; bh=pS0MHbEiTw9KXRiEpd5CeLRAl4oXVL8Oft6cJCAu4mg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=emdx7L4BkiLOYVbCfAq+UXbuiOECEFZ/cvmr92CdFe/0GA8CDWj+Kuiei57Ax2iAp e7FwzssWMYSqdWhw3rBY1K/J6l4N0m8+T1UskDGWsCcPPiASIgPaC6Y4NF34U/EEBC SAnH9L6WWav+krhkTARX5PTPORKwHMrFyQTRIBSOJvZZBbKwZ1oS+nAG8Q4DDyRj+L Qh5Jdf0kOXZ9UlJW6WmL6s1xbk+aqnuQSiBeCkzoGLIDcpGGGA09kzKetBed4Ut1HJ x9UKNse7OOO/eBd9QLL78rABwyGwm95J6IKpg2B1b8Ro9/odwCAyIxHXQ06ztiDswC WjMZQqOeVJwWw== From: Sasha Levin To: stable@vger.kernel.org Cc: "David Hildenbrand (Arm)" , Andrew Morton , syzbot+49b1021becba70c1f3f6@syzkaller.appspotmail.com, Nguyen Ngoc Thang , "Lorenzo Stoakes (ARM)" , "Mike Rapoport (Microsoft)" , Lance Yang , "Liam R. Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Benjamin Herrenschmidt , Peter Zijlstra , Rik van Riel , Sasha Levin Subject: [PATCH 6.1.y] mm: disallow ioremap'ing ordinary RAM in generic_access_phys() Date: Tue, 10 Nov 2026 11:50:04 -0500 Message-ID: <20261110164943.2527571-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107055432-failed-6.1-4590752e20aa@kernel.org> References: <20261107055432-failed-6.1-4590752e20aa@kernel.org> 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-Transfer-Encoding: 8bit From: "David Hildenbrand (Arm)" [ Upstream commit 4590752e20aa393cc0d4fe538c0747d14a98c97a ] 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: [ sashal: adapted PFN access and cleanup from follow_pfnmap helpers to the existing follow_pte() API ] Signed-off-by: Sasha Levin --- mm/memory.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/mm/memory.c b/mm/memory.c index 53334915fd4ad..2fafde251077c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5644,6 +5644,7 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, resource_size_t phys_addr; unsigned long prot = 0; void __iomem *maddr; + struct page *page; pte_t *ptep, pte; spinlock_t *ptl; int offset = offset_in_page(addr); @@ -5656,6 +5657,19 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, if (follow_pte(vma->vm_mm, addr, &ptep, &ptl)) return -EINVAL; pte = *ptep; + + /* + * 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(pte_pfn(pte)); + if (page && !PageReserved(page)) { + pte_unmap_unlock(ptep, ptl); + return -EINVAL; + } + pte_unmap_unlock(ptep, ptl); prot = pgprot_val(pte_pgprot(pte)); -- 2.53.0