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[2003:cb:c709:d500:4044:6d4c:f060:f677]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3502b8a77easm34985826f8f.53.2024.05.22.13.25.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 May 2024 13:25:57 -0700 (PDT) Message-ID: Date: Wed, 22 May 2024 22:25:55 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: 6.10/bisected/regression - commit 8430557fc584 cause warning at mm/page_table_check.c:198 __page_table_check_ptes_set+0x306 To: Peter Xu Cc: Mikhail Gavrilov , Pavel Tatashin , axelrasmussen@google.com, nadav.amit@gmail.com, Andrew Morton , Linux Memory Management List , Linux List Kernel Mailing References: <03faa624-1685-4a21-81fc-cc9e8b760e97@redhat.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: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 6DA6540003 X-Rspam-User: X-Rspamd-Server: rspam12 X-Stat-Signature: oy8fc4jjztfe15kkuk59up75iqznkjdt X-HE-Tag: 1716409562-519058 X-HE-Meta: U2FsdGVkX1/AHy1pmwY3BFiTSB+/oGIsZhmQeRS5Kewz1JTnVPPNbveAPeH8ddEDyauq2fMCVCeC0AZjezm1A6Q+ulVIhuq+ItopnNI2bypBpKrdq4SwloK7D34WdzAEC9/04o7wURfwr2RJFF9LSBj6RjHM+yeaA7aWVItGLstld7Sfy/fobzHGamEag6aCUk5QlOkqiOoTirhQrhy5y1vLscnbXKdCohfOHMSVRkrCojs2NA53OsphHQcJsXMtZU49FNRSmxyIhqd2EFEmeaW88Ix+Fw7By8NiortDplU9cwoUKA1ElquIyV+aRHkly6NumoNiAIGGRVCX+6IMxXNl1acnUImELBonbOEV0FcagR/Q2DNWPPKRhxjVuFYoeAKkfcw2zny2C6tLVH73a4vVpJopy+gNiPWSed2z9fYcy9D52Uv0ONObmnB15EF+iWF4Mt8d1ovXypcowvFee7ysZrYLbGpq/+jEk1uSZUq0llDE9MhTmfIyxES9LStnhEYC8pPBevc2s/Z4xSPjZ7K5M7TysxlwH3VTqVJCS5zE1IA16WKHRX/ffLmZpK3s3lCR65cv/jqIqI+hfbW5td9ctK77cydRK8eDlkWwezLQZHnXckisbOS/4uhUdJyqhsOA6PD0e8Ii/YSjjYl20w2+bZuySXkfeAVUVLLmmymY4Ba6rsvjNADPXo0a2j+VvQf/9PMSFsNP1GesvHgiwsD3OAHmrnVvPP78Z8WejULUVE3v/e1BPu8k4bvvaRoAUM30L4QWLcp1OaF9MnGY1hQXmizQc5e0diVqTSbVccBc/TU+9BvbWcTOVWG9GfqYAL61FVVnoTs4RZB3GOSVC+At+jlQaAWswjYrtSQvQb8tG6PzObFQQl9GA6LGxCDVJwVqziZNMu2j64KhVc8m4trZ2rrpaInPXkhq82Uz2S9lQDvLsO1wiRP3KOv6quYUpaviSxxZuBFKkWX4aGe 2csdSauP yM6k2gml5I63RYnpzfX5uyztzUSG/+1Vzs50IVL6Q1qUpWKi6tKGWr+ojnLXhYQZGbw9aUO4KNJIwa1M+s98lCqQoYoNQp9Q1UHj59CA6lnlnpA+uWP5xZNfjh+drXtB0hZIPQIPP9M647dNl3geixyLy23uYWWWvbIZatyAsiMWoRAfc0QlxUMH0GOiEF2azDdouVUj2theYRIFuk1oieEUCmX6W3NL19Qz6P/OMvrxd1OlcRqjgnqq2jugtto54CLz6QrgD+BJWIbAdYtVQSHePWA5pte8IOc7xSsHeVNiOZRlQJFy4g8B4w0UVTMHe7WkS2Abwef8czLit6QowMwHm15H7pB1rDrwmKKagaJqlmJTW3iPmrCOz/zy/YHlGsEY7qEGwkBMfh7yvL5PCqZAeTVLtpfz/J32iBM+sRJAwMeCxdjrBeriFKteRUTQSoWArCq9lXU5PtzDs6yW18i2No+cxtAX0aQPpSt/hHSqWHkk4+oCqjywUlUW6G2lbRu1Pnu5jNXPvzvQdnG3kZGm1ctC8MCx968My6hX/FmdhXDA2dzz0++6qLdSQV0n2U2u9n5wvZZrVh2EAKzVJd0G6rkBLZmrFGos7PQ6tA+H8rkh9tV9KCrfKV23Mb9JAq+tg 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 22.05.24 18:10, Peter Xu wrote: > On Wed, May 22, 2024 at 05:34:21PM +0200, David Hildenbrand wrote: >> On 22.05.24 17:18, Peter Xu wrote: >>> On Wed, May 22, 2024 at 09:48:51AM +0200, David Hildenbrand wrote: >>>> On 22.05.24 00:36, Peter Xu wrote: >>>>> On Wed, May 22, 2024 at 03:21:04AM +0500, Mikhail Gavrilov wrote: >>>>>> On Wed, May 22, 2024 at 2:37 AM Peter Xu wrote: >>>>>>> Hmm I still cannot reproduce. Weird. >>>>>>> >>>>>>> Would it be possible for you to identify which line in debug_vm_pgtable.c >>>>>>> triggered that issue? >>>>>>> >>>>>>> I think it should be some set_pte_at() but I'm not sure, as there aren't a >>>>>>> lot and all of them look benign so far. It could be that I missed >>>>>>> something important. >>>>>> >>>>>> I hope it's helps: >>>>> >>>>> Thanks for offering this, it's just that it doesn't look coherent with what >>>>> was reported for some reason. >>>>> >>>>>> >>>>>>> sh /usr/src/kernels/(uname -r)/scripts/faddr2line /lib/debug/lib/modules/(uname -r)/vmlinux debug_vm_pgtable+0x1c04 >>>>>> debug_vm_pgtable+0x1c04/0x3360: >>>>>> native_ptep_get_and_clear at arch/x86/include/asm/pgtable_64.h:94 >>>>>> (inlined by) ptep_get_and_clear at arch/x86/include/asm/pgtable.h:1262 >>>>>> (inlined by) ptep_clear at include/linux/pgtable.h:509 >>>>> >>>>> This is a pte_clear(), and pte_clear() shouldn't even do the set() checks, >>>>> and shouldn't stumble over what I added. >>>>> >>>>> IOW, it doesn't match with the real stack dump previously: >>>>> >>>>> [ 5.581003] ? __page_table_check_ptes_set+0x306/0x3c0 >>>>> [ 5.581274] ? __pfx___page_table_check_ptes_set+0x10/0x10 >>>>> [ 5.581544] ? __pfx_check_pgprot+0x10/0x10 >>>>> [ 5.581806] set_ptes.constprop.0+0x66/0xd0 >>>>> [ 5.582072] ? __pfx_set_ptes.constprop.0+0x10/0x10 >>>>> [ 5.582333] ? __pfx_pte_val+0x10/0x10 >>>>> [ 5.582595] debug_vm_pgtable+0x1c04/0x3360 >>>>> >>>> >>>> Staring at pte_clear_tests(): >>>> >>>> #ifndef CONFIG_RISCV >>>> pte = __pte(pte_val(pte) | RANDOM_ORVALUE); >>>> #endif >>>> set_pte_at(args->mm, args->vaddr, args->ptep, pte); >>>> >>>> So we set random PTE bits, probably setting the present, uffd and write bit >>>> at the same time. That doesn't make too much sense when we want to perform >>>> that such combinations cannot exist. >>> >>> Here the issue is I don't think it should set W bit anyway, as we init >>> page_prot to be RWX but !shared: >>> >>> args->page_prot = vm_get_page_prot(VM_ACCESS_FLAGS); >>> >>> On x86_64 (Mikhail's system) it should have W bit cleared afaict, meanwhile >>> the RANDOM_ORVALUE won't touch bit W due to S390_SKIP_MASK (which contains >>> bit W / bit 1, which is another "accident"..). Then even if with that it >>> should not trigger.. I think that's also why I cannot reproduce this >>> problem locally. >> >> Why oh why are skip mask applied independently of the architecture. >> >> While _PAGE_RW should indeed be masked out by RANDOM_ORVALUE. >> >> But with shadow stacks we consider a PTE writable (see >> pte_write()->pte_shstk()) if >> (1) X86_FEATURE_SHSTK is enabled >> (2) _PAGE_RW is clear >> (3) _PAGE_DIRTY is set >> >> _PAGE_DIRTY is bit 6. >> >> Likely your CPU does not support shadow stacks. > > Good point. My host has it, but I tested in the VM which doesn't. I > suppose we can wait and double check whether Mikhail should see the issue > went away with that patch provided. > > In this case, instead of keep fiddling with random bits to apply and > further work on top of per-arch random bits, I'd hope we can simply drop > that random mechanism as I don't think it'll be pxx_none() now. I attached > a patch I plan to post. Does it look reasonable? I doubt that randomness ever helped in finding a BUG. Clearing is just too simple ... but I might just be wrong :) I'd vote for removing that, this will likely not be the last issue we run into once we add more sanity checks during set_pte_at(). -- Cheers, David / dhildenb