From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 695BF271468; Mon, 9 Mar 2026 16:47:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773074855; cv=none; b=uaLxTFeJdcdFPWQa78hCsa7H9UYjLmCa5TdCu8dn8RAw3zuZsY41sG6LIbFYBJx2YqkM39ZbvBFo+AcO51o9CINZ7JkjmmO1dr9cJ+t3WZpfopRdLlwv4/BoVWe4GJ5a81ZESBY4C8WoSI2TaxPZXkEH6uOwOzKet1/pUEp3fJ4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773074855; c=relaxed/simple; bh=w0oBKdjbNxuaeDRrRHZ7GwNRlXTe6xkr+Bdf92ElWpM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=cFOK+hVn2uXPDP223lXuaXe2j4kG6fzerodUTh8h97WXd0Kb6Mkcg0Gy9Itjewc2s0bvnCGVbOfMqnt3ZN87Rch9ABoeRT1urI0Jej2N59x7G67uwkC+nszVQoHAgdTv1gDFV4wNT0epAvShhHLuCFGuIc3TiV5FZP7DVRg4tIQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bd5kx7Iv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bd5kx7Iv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 89C74C4CEF7; Mon, 9 Mar 2026 16:47:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773074855; bh=w0oBKdjbNxuaeDRrRHZ7GwNRlXTe6xkr+Bdf92ElWpM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; 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 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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