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(p200300cbc7404b007ba7a10929b8e459.dip0.t-ipconnect.de. [2003:cb:c740:4b00:7ba7:a109:29b8:e459]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-371898ab469sm11356901f8f.100.2024.08.19.13.24.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 19 Aug 2024 13:24:44 -0700 (PDT) Message-ID: Date: Mon, 19 Aug 2024 22:24:42 +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: Michal Hocko 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, 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, Christoph Hellwig , 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> <5424dfa3-03db-4a82-a08e-fb31285774b3@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-Stat-Signature: yeifg4ft5pt78rzcq7de3km5g6g4jo44 X-Rspamd-Queue-Id: 8E30480005 X-Rspamd-Server: rspam11 X-HE-Tag: 1724099089-969536 X-HE-Meta: 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 M4nAKloN 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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 19:12, Michal Hocko wrote: > On Mon 19-08-24 14:49:55, David Hildenbrand wrote: >> On 19.08.24 14:48, Barry Song wrote: > [...] >>>>>>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>>>>>>>> index 60742d057b05..d2c37f8f8d09 100644 >>>>>>>>> --- a/mm/page_alloc.c >>>>>>>>> +++ b/mm/page_alloc.c >>>>>>>>> @@ -4668,8 +4668,10 @@ struct page *__alloc_pages_noprof(gfp_t gfp, unsigned int order, >>>>>>>>> * There are several places where we assume that the order value is sane >>>>>>>>> * so bail out early if the request is out of bound. >>>>>>>>> */ >>>>>>>>> - if (WARN_ON_ONCE_GFP(order > MAX_PAGE_ORDER, gfp)) >>>>>>>>> + if (WARN_ON_ONCE_GFP(order > MAX_PAGE_ORDER, gfp)) { >>>>>>>>> + BUG_ON(gfp & __GFP_NOFAIL); >>>>>>>>> return NULL; >>>>>>>>> + } > [...] >>> Returning NULL doesn't necessarily crash the caller's process, p->field, >>> *(p + offset) deference could be used by hackers to exploit the system. >> >> See my other reply to Michal: why do we even allow to specify them >> separately and not simply let one enforce the other? > > Are you replying to this patch? This is not about a combination of > flags. This is about the above (and other similar) boundary checks which > return NULL if the size is deemed incorrect. > I think those are potential > problems because it could be a lack of input check which could be turned > into a potentially malicious code. Because unchecked (return value > because NOFAIL never fails, right?) return value might even not OOPs and > become a silent read/write into memory. Right, that's a different kind of issue than the simple "don't pass stupid flag combinations" thing where "we'll fix that up for you" is more reasonable. Possibly NOFAIL allocations with an allocation sizes that is not a small compile-time constant already has a bad smell to it, but I'm sure there are reasonable exceptions ... > > Whether to BUG_ON or simply loop for ever in the allocator if somebody > requests non-sleeping NOFAIL allocation is a different story. Right, "warn + loop forever" is one alternative where you could at least keep the system alive to some degree. Satisfying a large allocation might take a long time, satisfying a "too large" allocation would take forever. But as Linus says, it's all workarounds for other buggy code, to make buggy code less exploitable, maybe, ... -- Cheers, David / dhildenb