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[149.14.88.26]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4b2b8de5fdesm85480771cf.31.2025.08.27.02.38.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Aug 2025 02:38:57 -0700 (PDT) Message-ID: <66dac672-88f8-4101-9a66-382cd3794756@redhat.com> Date: Wed, 27 Aug 2025 11:38:53 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] mm/swap: add BUG_ON(folio==NULL) to folios_put_refs() To: Max Kellermann , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, shikemeng@huaweicloud.com, kasong@tencent.com, nphamcs@gmail.com, bhe@redhat.com, chrisl@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250826231626.218675-1-max.kellermann@ionos.com> <20250826231626.218675-2-max.kellermann@ionos.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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20250826231626.218675-2-max.kellermann@ionos.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: os2QP6V2Vn-AZ6ypPXy1TwYuqIzA4cYA8LDdH1MiWf4_1756287538 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: E9B6840005 X-Stat-Signature: cna7axp3mbpmcm7fiqugb59xo6emkk1f X-Rspam-User: X-HE-Tag: 1756287540-691222 X-HE-Meta: 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 MzIvGr3D 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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 27.08.25 01:16, Max Kellermann wrote: > It is not legal to have NULL pointers in a folio_batch. > > However, the Ceph code does exactly this, and a refactoring patch gone > wrong has exposed this to folios_put_refs(), see > https://lore.kernel.org/ceph-devel/aK4v548CId5GIKG1@swift.blarg.de/ > > I believe this should Oops instead of crashing due to NULL pointer > reference (guarded by is_huge_zero_folio(), which may silently hide > the bug). > > Signed-off-by: Max Kellermann > --- > mm/swap.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/swap.c b/mm/swap.c > index 3632dd061beb..07ccda00e7ee 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -952,6 +952,7 @@ void folios_put_refs(struct folio_batch *folios, unsigned int *refs) > for (i = 0, j = 0; i < folios->nr; i++) { > struct folio *folio = folios->folios[i]; > unsigned int nr_refs = refs ? refs[i] : 1; > + BUG_ON(folio == NULL); We shouldn't be adding such checks into each and every function that expects a valid folio. The is_huge_zero_folio() is special because it does not crash immediately when the function is abused. So we don't want this (and in particular not a BUG_ON). -- Cheers David / dhildenb