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Tue, 14 May 2024 13:46:46 -0700 (PDT) Message-ID: <74a72eeb-122f-453e-baa7-63504e7c4bd8@redhat.com> Date: Tue, 14 May 2024 22:46:44 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/ksm: fix possible UAF of stable_node To: Chengming Zhou , Andrew Morton , Hugh Dickins , Andrea Arcangeli , Stefan Roesch Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, zhouchengming@bytedance.com References: <20240513-b4-ksm-stable-node-uaf-v1-1-f687de76f452@linux.dev> 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: <20240513-b4-ksm-stable-node-uaf-v1-1-f687de76f452@linux.dev> 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-Queue-Id: AAF73160014 X-Stat-Signature: bwjnpfigyra9qau93b44b65edcfutpm5 X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1715719610-510653 X-HE-Meta: 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 voSf5riF 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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 13.05.24 05:07, Chengming Zhou wrote: > The commit 2c653d0ee2ae ("ksm: introduce ksm_max_page_sharing per page > deduplication limit") introduced a possible failure case in the > stable_tree_insert(), where we may free the new allocated stable_node_dup > if we fail to prepare the missing chain node. > > Then that kfolio return and unlock with a freed stable_node set... And > any MM activities can come in to access kfolio->mapping, so UAF. > > Fix it by moving folio_set_stable_node() to the end after stable_node > is inserted successfully. > > Fixes: 2c653d0ee2ae ("ksm: introduce ksm_max_page_sharing per page deduplication limit") > Signed-off-by: Chengming Zhou > --- > mm/ksm.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/ksm.c b/mm/ksm.c > index e1034bf1c937..a8b76af5cf64 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -2153,7 +2153,6 @@ static struct ksm_stable_node *stable_tree_insert(struct folio *kfolio) > > INIT_HLIST_HEAD(&stable_node_dup->hlist); > stable_node_dup->kpfn = kpfn; > - folio_set_stable_node(kfolio, stable_node_dup); > stable_node_dup->rmap_hlist_len = 0; > DO_NUMA(stable_node_dup->nid = nid); > if (!need_chain) { > @@ -2172,6 +2171,8 @@ static struct ksm_stable_node *stable_tree_insert(struct folio *kfolio) > stable_node_chain_add_dup(stable_node_dup, stable_node); > } > > + folio_set_stable_node(kfolio, stable_node_dup); > + > return stable_node_dup; Looks correct to me. We might now link the node before the folio->mapping is set up. Do we care? Don't think so. Acked-by: David Hildenbrand -- Cheers, David / dhildenb