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Mon, 22 Mar 2021 13:20:28 -0700 (PDT) MIME-Version: 1.0 References: <20210322175132.36659-1-peterx@redhat.com> In-Reply-To: <20210322175132.36659-1-peterx@redhat.com> From: Axel Rasmussen Date: Mon, 22 Mar 2021 13:19:50 -0700 Message-ID: Subject: Re: [PATCH] userfaultfd/hugetlbfs: Fix minor fault page leak To: Peter Xu Cc: Linux MM , LKML , Andrew Morton , Andrea Arcangeli , Mike Kravetz , Mike Rapoport Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: eza34a7o8jxzp6gxyctrc7duwj6kpcx1 X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 14808C0042E3 Received-SPF: none (google.com>: No applicable sender policy available) receiver=imf22; identity=mailfrom; envelope-from=""; helo=mail-il1-f178.google.com; client-ip=209.85.166.178 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1616444438-432158 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 Mon, Mar 22, 2021 at 10:51 AM Peter Xu wrote: > > When uffd-minor enabled, we need to put the page cache before handling the > userfault in hugetlb_no_page(), otherwise the page refcount got leaked. > > This can be reproduced by running userfaultfd selftest with hugetlb_shared > mode, then cat /proc/meminfo. > > Cc: Axel Rasmussen > Cc: Andrea Arcangeli > Cc: Mike Kravetz > Cc: Mike Rapoport > Cc: Andrew Morton > Fixes: f2bf15fb0969 ("userfaultfd: add minor fault registration mode") > Signed-off-by: Peter Xu > --- > mm/hugetlb.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 408dbc08298a..56b78a206913 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -4449,6 +4449,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, > /* Check for page in userfault range. */ > if (userfaultfd_minor(vma)) { > unlock_page(page); > + put_page(page); > ret = hugetlb_handle_userfault(vma, mapping, idx, > flags, haddr, > VM_UFFD_MINOR); > -- > 2.26.2 > Thanks for the fix, Peter! I applied the patch and verified it does indeed fix the issue. Reviewed-by: Axel Rasmussen