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[2003:cb:c741:c700:3db9:94c9:28b0:34f2]) by smtp.gmail.com with ESMTPSA id fm5-20020a05600c0c0500b004148f012abdsm1709298wmb.6.2024.03.26.05.32.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 26 Mar 2024 05:32:20 -0700 (PDT) Message-ID: Date: Tue, 26 Mar 2024 13:32:19 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 2/3] selftests/memfd_secret: add vmsplice() test To: Mike Rapoport Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Miklos Szeredi , Lorenzo Stoakes , xingwei lee , yue sun References: <20240325134114.257544-1-david@redhat.com> <20240325134114.257544-3-david@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: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 807C5C0009 X-Stat-Signature: xjmm6xwcre7noaijapzq14zysjegh8gs X-HE-Tag: 1711456346-590712 X-HE-Meta: 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 LwjFgtOy 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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 26.03.24 07:17, Mike Rapoport wrote: > Hi David, > > On Mon, Mar 25, 2024 at 02:41:13PM +0100, David Hildenbrand wrote: >> Let's add a simple reproducer for a scneario where GUP-fast could succeed >> on secretmem folios, making vmsplice() succeed instead of failing. The >> reproducer is based on a reproducer [1] by Miklos Szeredi. >> >> Perform the ftruncate() only once, and check the return value. >> >> For some reason, vmsplice() reliably fails (making the test succeed) when >> we move the test_vmsplice() call after test_process_vm_read() / >> test_ptrace(). > > That's because ftruncate() call was in test_remote_access() and you need it > to mmap secretmem. I don't think that's the reason. I reshuffled the code a couple of times without luck. And in fact, even executing the vmsplice() test twice results in the second iteration succeeding on an old kernel (6.7.4-200.fc39.x86_64). ok 1 mlock limit is respected ok 2 file IO is blocked as expected not ok 3 vmsplice is blocked as expected ok 4 vmsplice is blocked as expected ok 5 process_vm_read is blocked as expected ok 6 ptrace is blocked as expected Note that the mmap()+memset() succeeded. So the secretmem pages should be in the page table. Even weirder, if I simply mmap()+memset()+munmap() secretmem *once*, the test passes diff --git a/tools/testing/selftests/mm/memfd_secret.c b/tools/testing/selftests/mm/memfd_secret.c index 0acbdcf8230e..7a973ec6ac8f 100644 --- a/tools/testing/selftests/mm/memfd_secret.c +++ b/tools/testing/selftests/mm/memfd_secret.c @@ -96,6 +96,14 @@ static void test_vmsplice(int fd) return; } + mem = mmap(NULL, page_size, prot, mode, fd, 0); + if (mem == MAP_FAILED) { + fail("Unable to mmap secret memory\n"); + goto close_pipe; + } + memset(mem, PATTERN, page_size); + munmap(mem, page_size); + mem = mmap(NULL, page_size, prot, mode, fd, 0); if (mem == MAP_FAILED) { fail("Unable to mmap secret memory\n"); ok 1 mlock limit is respected ok 2 file IO is blocked as expected ok 3 vmsplice is blocked as expected ok 4 process_vm_read is blocked as expected ok 5 ptrace is blocked as expected ... could it be that munmap()+mmap() will end up turning these pages into LRU pages? I am 100% sure that is happening -- likely, because VM_LOCKED is involved, because on the patched kernel, I see the following: ok 1 mlock limit is respected ok 2 file IO is blocked as expected ok 3 vmsplice is blocked as expected not ok 4 vmsplice is blocked as expected ok 5 process_vm_read is blocked as expected ok 6 ptrace is blocked as expected At this point, I think we should remove the LRU test for secretmem. I'll adjust patch #1 and extend this test to cover that case as well. > >> Properly cleaning up in test_remote_access(), which is not >> part of this change, won't change that behavior. Therefore, run the >> vmsplice() test for now first -- something is a bit off once we involve >> fork(). >> >> [1] https://lkml.kernel.org/r/CAJfpegt3UCsMmxd0taOY11Uaw5U=eS1fE5dn0wZX3HF0oy8-oQ@mail.gmail.com >> >> Signed-off-by: David Hildenbrand >> --- >> tools/testing/selftests/mm/memfd_secret.c | 44 +++++++++++++++++++++-- >> 1 file changed, 42 insertions(+), 2 deletions(-) >> >> diff --git a/tools/testing/selftests/mm/memfd_secret.c b/tools/testing/selftests/mm/memfd_secret.c >> index 9b298f6a04b3..0acbdcf8230e 100644 >> --- a/tools/testing/selftests/mm/memfd_secret.c >> +++ b/tools/testing/selftests/mm/memfd_secret.c >> @@ -20,6 +20,7 @@ >> #include >> #include >> #include >> +#include >> >> #include "../kselftest.h" >> >> @@ -83,6 +84,43 @@ static void test_mlock_limit(int fd) >> pass("mlock limit is respected\n"); >> } >> >> +static void test_vmsplice(int fd) >> +{ >> + ssize_t transferred; >> + struct iovec iov; >> + int pipefd[2]; >> + char *mem; >> + >> + if (pipe(pipefd)) { >> + fail("pipe failed: %s\n", strerror(errno)); >> + return; >> + } >> + >> + mem = mmap(NULL, page_size, prot, mode, fd, 0); >> + if (mem == MAP_FAILED) { >> + fail("Unable to mmap secret memory\n"); >> + goto close_pipe; >> + } >> + >> + /* >> + * vmsplice() may use GUP-fast, which must also fail. Prefault the >> + * page table, so GUP-fast could find it. >> + */ >> + memset(mem, PATTERN, page_size); >> + >> + iov.iov_base = mem; >> + iov.iov_len = page_size; >> + transferred = vmsplice(pipefd[1], &iov, 1, 0); >> + >> + ksft_test_result(transferred < 0 && errno == EFAULT, >> + "vmsplice is blocked as expected\n"); > > The same message will be printed on success and on failure. > > I think > > if (transferred < 0 && errno == EFAULT) > pass("vmsplice is blocked as expected"); > else > fail("vmsplice: unexpected memory acccess"); > > is clearer than feeding different strings to ksft_test_result(). > Can do, thanks! -- Cheers, David / dhildenb