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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id 00721157ae682-798decec989sm38049157b3.16.2026.03.08.19.08.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 08 Mar 2026 19:09:00 -0700 (PDT) Date: Sun, 8 Mar 2026 19:08:46 -0700 (PDT) From: Hugh Dickins To: Jianhui Zhou 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 Subject: Re: [PATCH v2] mm/userfaultfd: fix hugetlb fault mutex hash calculation In-Reply-To: <20260307143542.179953-1-jianhuizzzzz@gmail.com> Message-ID: References: <20260306140332.171078-1-jianhuizzzzz@gmail.com> <20260307143542.179953-1-jianhuizzzzz@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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_hugetlb 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