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[178.24.249.8]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a83839464ebsm626866766b.155.2024.08.19.06.14.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 19 Aug 2024 06:14:14 -0700 (PDT) Message-ID: <6b24cb47-c48f-4ceb-93c9-ad8732e4222e@redhat.com> Date: Mon, 19 Aug 2024 15:14:12 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/4] mm: BUG_ON to avoid NULL deference while __GFP_NOFAIL fails To: Christoph Hellwig Cc: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org, 42.hyeyoo@gmail.com, cl@linux.com, hailong.liu@oppo.com, hch@infradead.org, iamjoonsoo.kim@lge.com, mhocko@suse.com, penberg@kernel.org, rientjes@google.com, roman.gushchin@linux.dev, torvalds@linux-foundation.org, urezki@gmail.com, v-songbaohua@oppo.com, vbabka@suse.cz, virtualization@lists.linux.dev, Lorenzo Stoakes , Kees Cook , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Jason Wang , Maxime Coquelin , "Michael S. Tsirkin" , Xuan Zhuo References: <20240817062449.21164-1-21cnbao@gmail.com> <20240817062449.21164-4-21cnbao@gmail.com> <5654b71c-1d9d-4c48-b28b-664662da8897@redhat.com> <416ac265-ced2-4f90-a347-0a256edf7fdf@redhat.com> <54a4619d-e826-465e-9a0f-0a8f37798e15@redhat.com> <20240819124924.GA7642@lst.de> <20240819125346.GA7992@lst.de> 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: <20240819125346.GA7992@lst.de> 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-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 3077510000F X-Stat-Signature: ogsmawgdi35kjgtg5bp38kpf4q6oxbja X-Rspam-User: X-HE-Tag: 1724073259-103455 X-HE-Meta: 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 Go2TOx+x 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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 19.08.24 14:53, Christoph Hellwig wrote: > On Mon, Aug 19, 2024 at 02:51:06PM +0200, David Hildenbrand wrote: >> On 19.08.24 14:49, Christoph Hellwig wrote: >>> On Mon, Aug 19, 2024 at 02:33:06PM +0200, David Hildenbrand wrote: >>>> It should all be caught during testing either way. And if some OOT module >>>> does something nasty, that's not our responsibility. >>>> >>>> BUG_ON is not a way to write assertions into the code. >>> >>> So you'd rather create exploits than crashing on a fundamental API >>> violation? That's exactly what the series is trying to fix. >> >> I'd rather have a sane API that doesn't even allow this level of >> flexibility with NOFAIL. >> >> But probably I'm missing more details here why this all has to be so >> complicated ;) > > Well, the only way to do that is to remove (__)GFP_NOFAIL and require > either explicit _nofail variants without a way to pass gfp flags, or > endless loops in the callers. I suggested the first one earlier, but > no one liked it due to the API complexity and overhead. And I've not > heard anyone arguing for the latter yet. Right, and and "allocate more than even possible" case is extremely ugly. > > One other way might be a compile time check that requires any GPF > flag that contains (__)GFP_NOFAIL to be a compile time constants. > This is true for many but not all callers currently. Right. -- Cheers, David / dhildenb