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[2003:d8:2f30:ec00:8f7e:58a4:ebf0:6a36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a4eac8ad8csm1037620f8f.55.2025.05.28.02.59.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 28 May 2025 02:59:57 -0700 (PDT) Message-ID: Date: Wed, 28 May 2025 11:59:56 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: fix COW mapping handing in generic_access_phys From: David Hildenbrand 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> <0d4f0180-52e6-47c9-b141-54e7e7c86880@redhat.com> 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: <0d4f0180-52e6-47c9-b141-54e7e7c86880@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: qvYKCWBacbFxRL_QcHnWeJPxkGQZN3P8sx02yWcnMkk_1748426398 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: 2A5731C000A X-Stat-Signature: 63ekunj4ofujbqchu63aon3k9eh4ra1e X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1748426403-672704 X-HE-Meta: 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 2u7bvNUq 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 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 10:59, David Hildenbrand wrote: > 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; > + } > + Thinking again, we might have a PMD/PUD mapping, so maybe follow_pfnmap_start() should really just refuse any refcounted pages. -- Cheers, David / dhildenb