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Tue, 15 Feb 2022 19:13:19 +0000 Received: from BY5PR10MB4196.namprd10.prod.outlook.com ([fe80::11f6:860e:575a:e6f1]) by BY5PR10MB4196.namprd10.prod.outlook.com ([fe80::11f6:860e:575a:e6f1%5]) with mapi id 15.20.4995.014; Tue, 15 Feb 2022 19:13:19 +0000 Message-ID: <1de73041-c8b9-d473-7ba3-22368f1dbf16@oracle.com> Date: Tue, 15 Feb 2022 11:13:16 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH v5 6/7] mm: userfaultfd: fix missing cache flush in mcopy_atomic_pte() and __mcopy_atomic() Content-Language: en-US To: Muchun Song , akpm@linux-foundation.org, zi.yan@cs.rutgers.edu, kirill.shutemov@linux.intel.com, rientjes@google.com, lars.persson@axis.com, ziy@nvidia.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, duanxiongchun@bytedance.com, fam.zheng@bytedance.com References: <20220210123058.79206-1-songmuchun@bytedance.com> <20220210123058.79206-7-songmuchun@bytedance.com> From: Mike Kravetz In-Reply-To: <20220210123058.79206-7-songmuchun@bytedance.com> Content-Type: text/plain; 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dkim=pass header.d=oracle.com header.s=corp-2021-07-09 header.b=e6lvT0wG; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=niXpZQzL; dmarc=pass (policy=none) header.from=oracle.com; spf=none (imf16.hostedemail.com: domain of mike.kravetz@oracle.com has no SPF policy when checking 205.220.165.32) smtp.mailfrom=mike.kravetz@oracle.com X-HE-Tag: 1644952415-300667 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: On 2/10/22 04:30, Muchun Song wrote: > The userfaultfd calls mcopy_atomic_pte() and __mcopy_atomic() which do not > do any cache flushing for the target page. Then the target page will be > mapped to the user space with a different address (user address), which might > have an alias issue with the kernel address used to copy the data from the > user to. Fix this by insert flush_dcache_page() after copy_from_user() > succeeds. > > Fixes: b6ebaedb4cb1 ("userfaultfd: avoid mmap_sem read recursion in mcopy_atomic") > Fixes: c1a4de99fada ("userfaultfd: mcopy_atomic|mfill_zeropage: UFFDIO_COPY|UFFDIO_ZEROPAGE preparation") > Signed-off-by: Muchun Song > --- > mm/userfaultfd.c | 3 +++ > 1 file changed, 3 insertions(+) Reviewed-by: Mike Kravetz -- Mike Kravetz > > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c > index 0780c2a57ff1..6ccc534d1c1c 100644 > --- a/mm/userfaultfd.c > +++ b/mm/userfaultfd.c > @@ -150,6 +150,8 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm, > /* don't free the page */ > goto out; > } > + > + flush_dcache_page(page); > } else { > page = *pagep; > *pagep = NULL; > @@ -625,6 +627,7 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm, > err = -EFAULT; > goto out; > } > + flush_dcache_page(page); > goto retry; > } else > BUG_ON(page);