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[2003:d8:2f30:ec00:8f7e:58a4:ebf0:6a36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a4eac6e354sm916929f8f.10.2025.05.28.01.59.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 28 May 2025 01:59:54 -0700 (PDT) Message-ID: <0d4f0180-52e6-47c9-b141-54e7e7c86880@redhat.com> Date: Wed, 28 May 2025 10:59:53 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: fix COW mapping handing in generic_access_phys To: Jinjiang Tu , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com Cc: linux-mm@kvack.org, wangkefeng.wang@huawei.com, Peter Xu References: <20250528015617.302681-1-tujinjiang@huawei.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20250528015617.302681-1-tujinjiang@huawei.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 3DxUyIYY3nHlg_f4mzOr4LfEzHuc_LmVCCi3Rk0CvmQ_1748422795 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 39F99A0008 X-Stat-Signature: nq4r9wsm1hy45ffpmimd9fqji9cqxj8q X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1748422799-86218 X-HE-Meta: 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 6jVvv2NH rSEbPqUSQHZOIqWsfyebRR0nDPKIw89det18Om5dmnH07amXXkGWDH7E8Xjah2fWyY9Dhw4nLKbz4XVFGJ10xrbSNtNblXXyyCNWn4+yS/hDhUwdR3gJwHiyjAJXR4xXI+DtICld6Gk7YvTJcenlooHmwynV/sHvzQavgjYIEcH1a0j/NnYIY9lx8N6xpOv/SMyIOs8U2+jO28pwlXh7vHMsHe2cGBDfcXtvJcGcL/8TXg0nOyxFiPEyb99avc+Ikob+on4IpQXrALz5euUWMTIgcEdnQcbui/y0XZTsY1SGURYgTab/MvADVj8LxkDmbOgSvH8vkEcM3OBkmTAMQ1w/TrIEa1+EBdgjjFfxg9YfeRAplTiV3mf3ujDGs9wqoW4z9BigLAr4dw2dL+2zI8FQ9ffYD7r3V15Y/UuzAj65llsgb+ydu25sIySYxqANROlxefZwsgocpKIi7Ev/1LyS8+VQFvqnY2WMwYHZNVzA9Iei2ohMCuHJQDjV7C2PPy6ltKk3nFXUA1+t3Syupcv6aCA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 28.05.25 03:56, Jinjiang Tu wrote: > Syzkaller reports a below BUG: > ioremap on RAM at 0x0000000022727000 - 0x0000000022727fff > WARNING: CPU: 3 PID: 3609 at arch/x86/mm/ioremap.c:216 __ioremap_caller+0x644/0x7f0 arch/x86/mm/ioremap.c:216 > Modules linked in: > CPU: 3 PID: 3609 Comm: syz.2.577 Not tainted 6.6.0+ #63 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 > RIP: 0010:__ioremap_caller+0x644/0x7f0 arch/x86/mm/ioremap.c:216 > Call Trace: > > generic_access_phys+0x241/0x480 mm/memory.c:6458 > __access_remote_vm+0x6af/0x970 mm/memory.c:6535 > access_process_vm+0x53/0x80 mm/memory.c:6600 > get_cmdline+0x192/0x380 mm/util.c:1041 > audit_log_proctitle kernel/auditsc.c:1620 [inline] > audit_log_exit+0x1424/0x18c0 kernel/auditsc.c:1811 > __audit_syscall_exit+0x252/0x2f0 kernel/auditsc.c:2079 > audit_syscall_exit include/linux/audit.h:356 [inline] > syscall_exit_work+0x10f/0x130 kernel/entry/common.c:166 > __syscall_exit_to_user_mode_work kernel/entry/common.c:205 [inline] > syscall_exit_to_user_mode+0x10/0x1e0 kernel/entry/common.c:218 > do_syscall_64+0x66/0x110 arch/x86/entry/common.c:87 > entry_SYSCALL_64_after_hwframe+0x78/0xe2 > > The /dev/mem is mapped with COW mapping, and mremap at the mm->args_start. > The special pfn mapping is replaced by anon folios due to COW. > generic_access_phys() is supposed to handle iomem, instead of RAM pfn, > thus trigger a WARN_ON. > > Similar to commit 04c35ab3bdae ("x86/mm/pat: fix VM_PAT handling in > COW mappings"). check if the pte is special to reject Cowed anon folios. > > Signed-off-by: Jinjiang Tu > --- > mm/memory.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/mm/memory.c b/mm/memory.c > index 49199410805c..e1dac84536ee 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -6840,6 +6840,13 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, > retry: > if (follow_pfnmap_start(&args)) > return -EINVAL; > + > + /* Never return PFNs of anon folios in COW mappings. */ > + if (!args.special) { > + follow_pfnmap_end(&args); > + return -EINVAL; > + } > + > prot = args.pgprot; > phys_addr = (resource_size_t)args.pfn << PAGE_SHIFT; > writable = args.writable; I assume we trigger this through vma->vm_ops->access, when the vm_ops have generic_access_phys set. I still dislike exposing the "special" bit here, as it is absolutely not what we should care about in the caller. In case our arch does not support pte_special, you fix will not catch that case ... The following might be better: diff --git a/mm/memory.c b/mm/memory.c index 37d8738f5e12e..810adb8d1a53b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -6681,6 +6681,14 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, prot = args.pgprot; phys_addr = (resource_size_t)args.pfn << PAGE_SHIFT; writable = args.writable; + + /* Refuse (refcounted) anonymous pages in CoW mappings. */ + if (is_cow_mapping(vma->vm_flags) && + vm_normal_page(vma, addr, ptep_get(args.ptep))) { + follow_pfnmap_end(&args); + return -EINVAL; + } + follow_pfnmap_end(&args); if ((write & FOLL_WRITE) && !writable) -- Cheers, David / dhildenb