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[2003:cb:c731:3d00:918f:ce94:4280:80f0]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-35dd04cb1e7sm9631143f8f.43.2024.06.03.13.15.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 03 Jun 2024 13:15:22 -0700 (PDT) Message-ID: <01d90f6c-64a1-4d25-a760-0d8865f6de95@redhat.com> Date: Mon, 3 Jun 2024 22:15:21 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/memory_hotplug: prevent accessing by index=-1 To: Fedor Pchelkin Cc: Anastasia Belova , lvc-project@linuxtesting.org, linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Oscar Salvador , linux-hardening@vger.kernel.org References: <20240603112830.7432-1-abelova@astralinux.ru> <3c2b1b1e-c9b3-442e-8f7b-5c7518d3fbdb@redhat.com> <20240603-4f7a5fd957aa1f9cbc8d5f14-pchelkin@ispras.ru> 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: <20240603-4f7a5fd957aa1f9cbc8d5f14-pchelkin@ispras.ru> 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-Stat-Signature: qtwimqrstswugio55ycpr55moiaobc5d X-Rspamd-Queue-Id: 3435B40011 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1717445727-222662 X-HE-Meta: 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 DfhowLLF eZkFsB/yAswt2eIVDuA2J4ZCWdHeGll8qGzAoXpYqHUKXV7KUkm5mpxqTZLTM2hOJOHmSsxk5ac0zAQjeVKGaK+ynq0qgsO7rpk4PE0a2V+NaSOhlzjN1dORLLMGRn5w3ySbTrnGeycf3ycRcKx2EX+ySWoz9ZzqgS203ogxLFaM85YsQZyIsJDWgVHGr4EoW5cIdZITQQnovIWLoFU85O5BLtfA9CPaB0DIfG3P3+TYCzDZLekKJeizO7Py4yJfbALKBc8Y6pnwNJ9BhOuNx7RupzLIRBeOy4cNlJoYTBm0VylQN5RHl4TL6neUvQ1/sxkePqiyUdtjafQcHeIc7YjC8CuqFeHF3evfjKY1JfXxJ3qcLXrdZReF7nIoUNoIsT7LgFdWDNlZElOZ2rV+FrtZR9LPSmRDjgmjEQY5/FwcR2ukRgulnrmLbkRIJmyga1dNnHh7xgpvLK1Df1aS7ho+I5jTP926DYKadQl6IwpXzIlwD8+Z20gGDmupdPqrTQWgSNXyk7WAtG96FBPhF/q1sGut9fhucn8OZ4YcCNiqYLnvzvRV47Jr8BuXixNkGA6QqbVXuQ098TGApcg2ukNdofPbwlmvCPrS8h2w9lDhMJgt/IDfdeHnCaKMOVdAezUEq 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 03.06.24 21:54, Fedor Pchelkin wrote: > On Mon, 03. Jun 18:07, David Hildenbrand wrote: >> On 03.06.24 13:28, Anastasia Belova wrote: >>> nid may be equal to NUMA_NO_NODE=-1. Prevent accessing node_data >>> array by invalid index with check for nid. >>> >>> Found by Linux Verification Center (linuxtesting.org) with SVACE. >>> >>> Fixes: e83a437faa62 ("mm/memory_hotplug: introduce "auto-movable" online policy") >>> Signed-off-by: Anastasia Belova >>> --- >>> mm/memory_hotplug.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >>> index 431b1f6753c0..bb98ee8fe698 100644 >>> --- a/mm/memory_hotplug.c >>> +++ b/mm/memory_hotplug.c >>> @@ -846,7 +846,7 @@ static bool auto_movable_can_online_movable(int nid, struct memory_group *group, >>> unsigned long kernel_early_pages, movable_pages; >>> struct auto_movable_group_stats group_stats = {}; >>> struct auto_movable_stats stats = {}; >>> - pg_data_t *pgdat = NODE_DATA(nid); >>> + pg_data_t *pgdat = (nid != NUMA_NO_NODE) ? NODE_DATA(nid) : NULL; >>> struct zone *zone; >>> int i; >> >> >> pgdat is never dereferenced when "nid == NUMA_NO_NODE". >> >> NODE_DATA is defined as >> >> arch/arm64/include/asm/mmzone.h:#define NODE_DATA(nid) (node_data[(nid)]) >> arch/loongarch/include/asm/mmzone.h:#define NODE_DATA(nid) (node_data[(nid)]) >> arch/mips/include/asm/mach-ip27/mmzone.h:#define NODE_DATA(n) (&__node_data[(n)]->pglist) >> arch/mips/include/asm/mach-loongson64/mmzone.h:#define NODE_DATA(n) (__node_data[n]) >> arch/powerpc/include/asm/mmzone.h:#define NODE_DATA(nid) (node_data[nid]) >> arch/riscv/include/asm/mmzone.h:#define NODE_DATA(nid) (node_data[(nid)]) >> arch/s390/include/asm/mmzone.h:#define NODE_DATA(nid) (node_data[nid]) >> arch/sh/include/asm/mmzone.h:#define NODE_DATA(nid) (node_data[nid]) >> arch/sparc/include/asm/mmzone.h:#define NODE_DATA(nid) (node_data[nid]) >> arch/x86/include/asm/mmzone_32.h:#define NODE_DATA(nid) (node_data[nid]) >> arch/x86/include/asm/mmzone_64.h:#define NODE_DATA(nid) (node_data[nid]) > > node_data array is declared as follows on most archs: > > struct pglist_data *node_data[MAX_NUMNODES]; > > It's an array of pointers to struct pglist_data. When doing node_data[-1], > it is actually dereferencing something before the start of the array in > order to obtain a pointer to struct pglist_data, isn't it? > > (C99, 6.5.2.1) The definition of the subscript operator [] is that > E1[E2] is identical to (*((E1)+(E2))). > Yes, you are right, I shouldn't have reviewed that on the subway :) I thought we'd have a "&" in the front ... What likely saves us here is the compiler doing the right thing, and not actually looking up that pointer when unused -- or even inlining auto_movable_can_online_movable() twice into auto_movable_zone_for_pfn(). [...] > > This code looks to be executed with memory_hotplug.online_policy=auto-movable, > I suppose it's not a real big problem due to the fact that node_data is a > global variable as otherwise [-1] array access would lead to crashes.. > > I've triggered the code with node_data[-1] on kernel with UBSAN enabled, > and no splats were observed. Is it due to that node_data is a global > variable or I somehow managed to misuse UBSAN for catching oob access? > Cc'ing linux-hardening. > > Nonetheless, maybe it'd be better to define pgdat inside the else-block > in auto_movable_can_online_movable() where it's only used? Yes, that's cleanest. And that's likely what the compiler does by itself already. Thanks! -- Cheers, David / dhildenb