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b=bd5kx7IvEw+rWYIKHq3E7XvsvgDedOF54tSeaPF602OgNkrcRDTPwIvNzJQmYbDUx mjfdD/dVFrI7IbeF+JtzM2opsHQI/I9hlKyO2rY1Cv7DtMJZvTaFGmCIZsddzEXx1+ If0adF4oyckIsmOU+HU/DjYWIDTbUR5RQQnQ8Nki5s0R4WWvf31AgP2vZlulGZAuUg k4cxHmvBzTJ1lKhizo3sdWE1d/rbvLwwoBHP2OSETJQH0rWxkAP6SGGe+UqIg2zIEr rhTvyc6kIDl/m1f+F2nqKsKoOuuCs9+pmONLeHAmOt79HVik66rLseCxRrFd9NP0L8 LAcX9dweDr9Sw== Message-ID: Date: Mon, 9 Mar 2026 17:47:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/userfaultfd: fix hugetlb fault mutex hash calculation To: Jianhui Zhou , Muchun Song , Oscar Salvador , Andrew Morton , Mike Rapoport Cc: Peter Xu , Andrea Arcangeli , Mike Kravetz , SeongJae Park , Jonas Zhou , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, syzbot+f525fd79634858f478e7@syzkaller.appspotmail.com References: <20260306140332.171078-1-jianhuizzzzz@gmail.com> <20260307143542.179953-1-jianhuizzzzz@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 1B95A40008 X-Stat-Signature: 3u4rib8swx3wqyuhp4zwmo7s7sn14onf X-Rspam-User: X-HE-Tag: 1773074855-66708 X-HE-Meta: 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 fOsysOSu 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/7/26 15:35, 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") > Reported-by: syzbot+f525fd79634858f478e7@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=f525fd79634858f478e7 > Cc: stable@vger.kernel.org > Signed-off-by: Jianhui Zhou > --- > v2: > - Remove unnecessary !CONFIG_HUGETLB_PAGE stub for vma_hugecache_offset() > (Peter Xu, SeongJae Park) > > include/linux/hugetlb.h | 11 +++++++++++ > mm/hugetlb.c | 11 ----------- > mm/userfaultfd.c | 5 ++++- > 3 files changed, 15 insertions(+), 12 deletions(-) > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index 65910437be1c..f003afe0cc91 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -796,6 +796,17 @@ static inline unsigned huge_page_shift(struct hstate *h) > return h->order + PAGE_SHIFT; > } > > +/* > + * Convert the address within this vma to the page offset within > + * the mapping, huge page units here. > + */ > +static inline pgoff_t vma_hugecache_offset(struct hstate *h, > + struct vm_area_struct *vma, unsigned long address) > +{ > + return ((address - vma->vm_start) >> huge_page_shift(h)) + > + (vma->vm_pgoff >> huge_page_order(h)); > +} It's hard to put my disgust about the terminology "hugecache" into words. Not your fault, but we should do better :) If you're starting to use that from other MM code then hugetlb.c, please find a better name. Further, I wonder whether we can avoid passing in "struct hstate *h" and simply call hstate_vma() internally. Something like the following to mimic linear_page_index() ? /** * hugetlb_linear_page_index - linear_page_index() but in hugetlb page * size granularity * @vma: ... * @address: ... * * Returns: ... */ static inline void hugetlb_linear_page_index(struct vm_area_struct *vma, unsigned long address) { struct hstate *h = hstate_vma(vma); ... } -- Cheers, David