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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id az23-20020a05600c601700b004054dcbf92asm2805042wmb.20.2023.11.16.01.19.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Nov 2023 01:19:14 -0800 (PST) Message-ID: Date: Thu, 16 Nov 2023 10:19:13 +0100 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [syzbot] [mm?] WARNING in unmap_page_range (2) To: Andrew Morton , syzbot , Muhammad Usama Anjum Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, usama.anjum@collabora.com, wangkefeng.wang@huawei.com, Peter Xu References: <000000000000b0e576060a30ee3b@google.com> <20231115140006.cc7de06f89b1f885f4583af0@linux-foundation.org> Content-Language: en-US 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: <20231115140006.cc7de06f89b1f885f4583af0@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 15.11.23 23:00, Andrew Morton wrote: > On Wed, 15 Nov 2023 05:32:19 -0800 syzbot wrote: > >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: ac347a0655db Merge tag 'arm64-fixes' of git://git.kernel.o.. >> git tree: upstream >> console+strace: https://syzkaller.appspot.com/x/log.txt?x=15ff3057680000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=287570229f5c0a7c >> dashboard link: https://syzkaller.appspot.com/bug?extid=7ca4b2719dc742b8d0a4 >> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=162a25ff680000 >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13d62338e80000 >> >> Downloadable assets: >> disk image: https://storage.googleapis.com/syzbot-assets/00e30e1a5133/disk-ac347a06.raw.xz >> vmlinux: https://storage.googleapis.com/syzbot-assets/07c43bc37935/vmlinux-ac347a06.xz >> kernel image: https://storage.googleapis.com/syzbot-assets/c6690c715398/bzImage-ac347a06.xz >> >> The issue was bisected to: >> >> commit 12f6b01a0bcbeeab8cc9305673314adb3adf80f7 >> Author: Muhammad Usama Anjum >> Date: Mon Aug 21 14:15:15 2023 +0000 >> >> fs/proc/task_mmu: add fast paths to get/clear PAGE_IS_WRITTEN flag > > Thanks. The bisection is surprising, but the mentioned patch does > mess with pagemap. > > How about we add this? > > From: Andrew Morton > Subject: mm/memory.c:zap_pte_range() print bad swap entry > Date: Wed Nov 15 01:54:18 PM PST 2023 > > We have a report of this WARN() triggering. Let's print the offending > swp_entry_t to help diagnosis. > > Link: https://lkml.kernel.org/r/000000000000b0e576060a30ee3b@google.com > Cc: Muhammad Usama Anjum > Signed-off-by: Andrew Morton > --- > > mm/memory.c | 1 + > 1 file changed, 1 insertion(+) > > --- a/mm/memory.c~a > +++ a/mm/memory.c > @@ -1521,6 +1521,7 @@ static unsigned long zap_pte_range(struc > continue; > } else { > /* We should have covered all the swap entry types */ > + pr_alert("unrecognized swap entry 0x%lx\n", entry.val); > WARN_ON_ONCE(1); > } > pte_clear_not_present_full(mm, addr, pte, tlb->fullmm); > _ > I'm curious if 1) make_uffd_wp_pte() won't end up overwriting existing pte markers, for example, if PTE_MARKER_POISONED is set. [unrelated to this bug] 2) We get the error on arm64, which does *not* support uffd-wp. Do we maybe end up calling make_uffd_wp_pte() and place a pte marker, even though we don't have CONFIG_PTE_MARKER_UFFD_WP? static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry) { #ifdef CONFIG_PTE_MARKER_UFFD_WP return is_pte_marker_entry(entry) && (pte_marker_get(entry) & PTE_MARKER_UFFD_WP); #else return false; #endif } Will always return false without CONFIG_PTE_MARKER_UFFD_WP. But make_uffd_wp_pte() might just happily place an entry. Hm. The following might fix the problem: diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 51e0ec658457..ae1cf19918d3 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1830,8 +1830,10 @@ static void make_uffd_wp_pte(struct vm_area_struct *vma, ptent = pte_swp_mkuffd_wp(ptent); set_pte_at(vma->vm_mm, addr, pte, ptent); } else { +#ifdef CONFIG_PTE_MARKER_UFFD_WP set_pte_at(vma->vm_mm, addr, pte, make_pte_marker(PTE_MARKER_UFFD_WP)); +#endif } } But I am *pretty* sure that that whole machinery should be fenced off. It does make 0 sense to mess with uffd-wp if there is no uffd-wp support. -- Cheers, David / dhildenb