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AJvYcCVK7jXgKcpzS3++arvHb1tYfi6ECT6W82Ji5Z5ysxhNbVz47o1yuuDx3kPdc8YZt735k+P1THA=@vger.kernel.org X-Gm-Message-State: AOJu0Yxrb9IhpGKF94M/6QYfXKgE/D+iX6ye+ta4iR/aBR+IGH9DUXkV LLHBT5ipeg6AYx+Q6kdB8DQbwfOlkjCwmU0JpeQXkGIeLCA3tWDOI7wXHLMXh/60WkPK9YbzYa8 aeSJNC0WmrIq2ehJakAeV97rCUtmRxuo= X-Gm-Gg: ATEYQzyUDo7d4zrzQgQyoMkE6HhELj4y6dNBG3h3ZtW0XlRW/U/Q8CFwiyLRQuUY7eH FCPpQNF3dX7jto5eFUNJipvBZ+T/IrG0BzxsM+yPQ7x7rFsLumQxYrGusVfKUBBJy81Pmro1ycV DhbGMvUjpTu6rdVgGcGhgpSlivX5S02cmIFmnn2efaHKt8Lsz56gm23MG7mjZpGc6WDNsXkiZmE UPnUHdObQMHFX2rzAMMtstwY5LAuwz4QFEmGJduTNCza3fAmsktSPzCv/dsXiHcsHXZrTPJPG3/ tG80Amr2DSZ7HweBYqT6iCeOyBUNXbvrd9URw2wOQA== X-Received: by 2002:a05:7300:b90b:b0:2be:6f6:a39c with SMTP id 5a478bee46e88-2be4dff28a3mr3189470eec.13.1773025720706; Sun, 08 Mar 2026 20:08:40 -0700 (PDT) Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20260306140332.171078-1-jianhuizzzzz@gmail.com> <20260307143542.179953-1-jianhuizzzzz@gmail.com> In-Reply-To: From: Jianhui Zhou Date: Mon, 9 Mar 2026 11:08:29 +0800 X-Gm-Features: AaiRm5345nQP7wJtt_NLhvQXt--b6XhTjz5lByTfdLY_4-yd1IfeVU4kfncXG9s Message-ID: Subject: Re: [PATCH v2] mm/userfaultfd: fix hugetlb fault mutex hash calculation To: Hugh Dickins Cc: Muchun Song , Oscar Salvador , Andrew Morton , Mike Rapoport , David Hildenbrand , Peter Xu , Andrea Arcangeli , Mike Kravetz , SeongJae Park , Jonas Zhou , Sidhartha Kumar , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, syzbot+f525fd79634858f478e7@syzkaller.appspotmail.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sun, Mar 08, 2026, Hugh Dickins wrote: > I have not thought it through, nor checked (someone else please do so > before this might reach stable trees); but I believe it's very likely > that that Fixes attribution to a 4.11 commit is wrong - more likely 6.7's > a08c7193e4f1 ("mm/filemap: remove hugetlb special casing in filemap.c"). You are right. Before a08c7193e4f1, linear_page_index() called linear_hugepage_index() for hugetlb VMAs, which returned the index in huge page units. The bug was introduced when a08c7193e4f1 removed that special casing but missed updating the caller in mm/userfaultfd.c. I will fix the Fixes tag in v3. Thanks! Hugh Dickins =E4=BA=8E2026=E5=B9=B43=E6=9C=889=E6=97=A5= =E5=91=A8=E4=B8=80 10:09=E5=86=99=E9=81=93=EF=BC=9A > > On Sat, 7 Mar 2026, Jianhui Zhou wrote: > > > In mfill_atomic_hugetlb(), linear_page_index() is used to calculate the > > page index for hugetlb_fault_mutex_hash(). However, linear_page_index() > > returns the index in PAGE_SIZE units, while hugetlb_fault_mutex_hash() > > expects the index in huge page units (as calculated by > > vma_hugecache_offset()). This mismatch means that different addresses > > within the same huge page can produce different hash values, leading to > > the use of different mutexes for the same huge page. This can cause > > races between faulting threads, which can corrupt the reservation map > > and trigger the BUG_ON in resv_map_release(). > > > > Fix this by replacing linear_page_index() with vma_hugecache_offset() > > and applying huge_page_mask() to align the address properly. To make > > vma_hugecache_offset() available outside of mm/hugetlb.c, move it to > > include/linux/hugetlb.h as a static inline function. > > > > Fixes: 60d4d2d2b40e ("userfaultfd: hugetlbfs: add __mcopy_atomic_hugetl= b for huge page UFFDIO_COPY") > > I have not thought it through, nor checked (someone else please do so > before this might reach stable trees); but I believe it's very likely > that that Fixes attribution to a 4.11 commit is wrong - more likely 6.7's > a08c7193e4f1 ("mm/filemap: remove hugetlb special casing in filemap.c"). > > Hugh