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Sat, 22 May 2021 19:45:48 -0700 (PDT) MIME-Version: 1.0 References: <20210521233952.236434-1-mike.kravetz@oracle.com> In-Reply-To: <20210521233952.236434-1-mike.kravetz@oracle.com> From: Muchun Song Date: Sun, 23 May 2021 10:45:11 +0800 Message-ID: Subject: Re: [External] [PATCH] userfaultfd: hugetlbfs: fix new flag usage in error path To: Mike Kravetz Cc: Linux Memory Management List , LKML , Oscar Salvador , Michal Hocko , Naoya Horiguchi , David Hildenbrand , Matthew Wilcox , Miaohe Lin , Mina Almasry , Andrew Morton , linux- stable Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=bytedance-com.20150623.gappssmtp.com header.s=20150623 header.b=fpn18oPM; dmarc=pass (policy=none) header.from=bytedance.com; spf=pass (imf14.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.210.169 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 5170DC0007F9 X-Stat-Signature: bxohcjeag6ahycd4obb4g3rmxowpsan9 X-HE-Tag: 1621737945-547860 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 Sat, May 22, 2021 at 7:40 AM Mike Kravetz wrote: > > In commit d6995da31122 ("hugetlb: use page.private for hugetlb specific > page flags") the use of PagePrivate to indicate a reservation count > should be restored at free time was changed to the hugetlb specific flag > HPageRestoreReserve. Changes to a userfaultfd error path as well as a > VM_BUG_ON() in remove_inode_hugepages() were overlooked. > > Users could see incorrect hugetlb reserve counts if they experience an > error with a UFFDIO_COPY operation. Specifically, this would be the > result of an unlikely copy_huge_page_from_user error. There is not an > increased chance of hitting the VM_BUG_ON. > > Fixes: d6995da31122 ("hugetlb: use page.private for hugetlb specific page flags") > Cc: > Signed-off-by: Mike Kravetz Reviewed-by: Muchun Song Thanks Mike.