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[2003:cb:c707:4d00:6ac5:30d:1611:918f]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-39c0b66a8c9sm14117975f8f.47.2025.04.01.07.37.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Apr 2025 07:37:52 -0700 (PDT) Message-ID: Date: Tue, 1 Apr 2025 16:37:51 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/7] mm/gup: check if both GUP_GET and GUP_PIN are set in __get_user_pages() earlier To: Baoquan He Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yanjun.zhu@linux.dev References: <20250331081327.256412-1-bhe@redhat.com> <20250331081327.256412-3-bhe@redhat.com> From: David Hildenbrand Content-Language: en-US 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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 01.04.25 16:34, Baoquan He wrote: > On 04/01/25 at 10:02am, David Hildenbrand wrote: >> On 31.03.25 10:13, Baoquan He wrote: >>> In __get_user_pages(), it will traverse page table and take a reference >>> to the page the given user address corresponds to if GUP_GET or GUP_PIN >>> is et. However, it's not supported both GUP_GET and GUP_PIN are set. >>> This check should be done earlier, but not doing it till entering into >>> follow_page_pte() and failed. >>> >>> Here move the checking to the beginning of __get_user_pages(). >>> >>> Signed-off-by: Baoquan He >>> --- >>> v1->v2: >>> - Fix code bug caused by copy-and-paste error, this is reported by >>> lkp test robot. >>> >>> mm/gup.c | 10 +++++----- >>> 1 file changed, 5 insertions(+), 5 deletions(-) >>> >>> diff --git a/mm/gup.c b/mm/gup.c >>> index 73777b1de679..f9bce14ed3cd 100644 >>> --- a/mm/gup.c >>> +++ b/mm/gup.c >>> @@ -847,11 +847,6 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, >>> pte_t *ptep, pte; >>> int ret; >>> - /* FOLL_GET and FOLL_PIN are mutually exclusive. */ >>> - if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == >>> - (FOLL_PIN | FOLL_GET))) >>> - return ERR_PTR(-EINVAL); >>> - >>> ptep = pte_offset_map_lock(mm, pmd, address, &ptl); >>> if (!ptep) >>> return no_page_table(vma, flags, address); >>> @@ -1434,6 +1429,11 @@ static long __get_user_pages(struct mm_struct *mm, >>> VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN))); >>> + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ >>> + if (WARN_ON_ONCE((gup_flags & (FOLL_PIN | FOLL_GET)) == >>> + (FOLL_PIN | FOLL_GET))) >>> + return -EINVAL; >>> + >> >> We already have that check in is_valid_gup_args(), that catches all external >> users that could possibly mess this up. > > Right. > >> >> So we can just convert that into a VM_WARN_ON_ONCE(), and while doing that, >> we should convert the VM_BUG_ON() above to a VM_WARN_ON_ONCE() as well. > > Sounds great to me, will put below change into this patch of v3 as suggested. > Thanks. > > diff --git a/mm/gup.c b/mm/gup.c > index 9e4ed09c578b..d551da9549b1 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1427,10 +1427,10 @@ static long __get_user_pages(struct mm_struct *mm, > > start = untagged_addr_remote(mm, start); > > - VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN))); > + VM_WARN_ON_ONCE(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN))); > > /* FOLL_GET and FOLL_PIN are mutually exclusive. */ > - if (WARN_ON_ONCE((gup_flags & (FOLL_PIN | FOLL_GET)) == > + if (VM_WARN_ON_ONCE((gup_flags & (FOLL_PIN | FOLL_GET)) == > (FOLL_PIN | FOLL_GET))) That won't work (or shouldn't work :) ). Just drop the handling, it's a sanity check we don't expect to ever trigger, just like the old VM_BUG_ON above. -- Cheers, David / dhildenb