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b=RzVo8jjCWjxbKTR0lq4p74IvclPrBtHc0dD6boesc39QJaNz4PlZn+6LQH1Mbcst+ 6Z8ynsaGqqGbItqtA8y89ryPQyb/BTsyh23/5cSpzmc4BvRsvS8/43kmPr0MVMBp2/ pnPQSdlh8lZQANoKTmmsTr/QU8xbguAK4lvXf0Uo= Date: Thu, 22 Feb 2024 13:00:05 -0800 From: Andrew Morton To: Qi Zheng Cc: aarcange@redhat.com, surenb@google.com, david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: userfaultfd: fix unexpected change to src_folio when UFFDIO_MOVE fails Message-Id: <20240222130005.c3f24eed1c1a27c66947e9df@linux-foundation.org> In-Reply-To: <20240222080815.46291-1-zhengqi.arch@bytedance.com> References: <20240222080815.46291-1-zhengqi.arch@bytedance.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 79E501C001A X-Rspam-User: X-Stat-Signature: 9cqpdm39t8bie3bhop88kx8od8ohbnms X-Rspamd-Server: rspam01 X-HE-Tag: 1708635611-536749 X-HE-Meta: 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 s6kbmKFy mFxWw 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: List-Subscribe: List-Unsubscribe: On Thu, 22 Feb 2024 16:08:15 +0800 Qi Zheng wrote: > After ptep_clear_flush(), if we find that src_folio is pinned we will fail > UFFDIO_MOVE and put src_folio back to src_pte entry, but the change to > src_folio->{mapping,index} is not restored in this process. This is not > what we expected, so fix it. > > Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI") What are the expected worst-case userspace-visible runtime effects of this flaw?