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AJvYcCVBr4jWr3RuXGxgnMWUlZGsawfOndbWiGc9dLodP6SjN+IJkUPsCyQp3pJwfcVQrPKvdcvxfhZV4X8BUT91//Z2yAA= X-Gm-Message-State: AOJu0YyLnwng5qf3se8tLfxcMs7/e54IjzptRqDq3mth8zvUkWQ74ZFo WDgHclM0uiLWPQbwMF6TOgP67wuxSMQPJIwQIz2w5xhd8AYPR/tEatIsFCkuZEaagroxGG5/i9u JlL0Yw8WaA54olouDkZJyvmXRZ/9ZoGbTbda8 X-Google-Smtp-Source: AGHT+IE5Cduia9Zqq/neFK9r466+MplB0k8dv91Jf+qZqUaukHu2rdbTtyZUd+6fF0kheatV3u2BeQ5qtuFLjjqN4+A= X-Received: by 2002:a05:690c:3388:b0:602:b697:dc60 with SMTP id fl8-20020a05690c338800b00602b697dc60mr472794ywb.50.1708638095219; Thu, 22 Feb 2024 13:41:35 -0800 (PST) MIME-Version: 1.0 References: <20240222080815.46291-1-zhengqi.arch@bytedance.com> In-Reply-To: From: Suren Baghdasaryan Date: Thu, 22 Feb 2024 13:41:22 -0800 Message-ID: Subject: Re: [PATCH] mm: userfaultfd: fix unexpected change to src_folio when UFFDIO_MOVE fails To: David Hildenbrand Cc: Qi Zheng , akpm@linux-foundation.org, aarcange@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 6220720006 X-Stat-Signature: 31okgx3mzs4h4adsr3odregh5ougpqnn X-HE-Tag: 1708638096-756725 X-HE-Meta: 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 Fmz/5OCr ehDVnjtt82kDetC80/KRiqQb7PnkOMdtHPV5yQ3GoRaNlMTjI9+ODQJcMAxN9QOhOnYzul34C2KDaOYTndajeyUftWq+n35dZAYhzVLXIRfym5/lTKyd/rNtyIQpOrGt9obicuo5j9fHlQnDlT3yoF+fWwFfwkCp5P6JlOtDFI9EWOUY2KqUx2o1A97OqjQL1ejg2QkFJHfnBU9o8JzkJn92glMItcaeAYZ4N77j+oZhm6M4xAgRQ4zFcBGtimINNvif41/XRw/crp+aM5LK4vfvF/COkujSZiLqrFEycCZ8aCULLb/r6FtIT+Ll1Td389hmldroyjqCnhQBuZwYsRZB0zehcF275lIax2g4y0BarmVRr02f5TVC+WQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, 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, Feb 22, 2024 at 12:43=E2=80=AFAM David Hildenbrand wrote: > > On 22.02.24 09:08, Qi Zheng wrote: > > After ptep_clear_flush(), if we find that src_folio is pinned we will f= ail > > 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") > > Signed-off-by: Qi Zheng > > --- > > mm/userfaultfd.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c > > index 4744d6a96f96..503ea77c81aa 100644 > > --- a/mm/userfaultfd.c > > +++ b/mm/userfaultfd.c > > @@ -1008,9 +1008,6 @@ static int move_present_pte(struct mm_struct *mm, > > goto out; > > } > > > > - folio_move_anon_rmap(src_folio, dst_vma); > > - WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr)= ); > > - > > orig_src_pte =3D ptep_clear_flush(src_vma, src_addr, src_pte); > > /* Folio got pinned from under us. Put it back and fail the move.= */ > > if (folio_maybe_dma_pinned(src_folio)) { > > @@ -1019,6 +1016,9 @@ static int move_present_pte(struct mm_struct *mm, > > goto out; > > } > > > > + folio_move_anon_rmap(src_folio, dst_vma); > > + WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr)= ); > > + > > orig_dst_pte =3D mk_pte(&src_folio->page, dst_vma->vm_page_prot); > > /* Follow mremap() behavior and treat the entry dirty after the m= ove */ > > orig_dst_pte =3D pte_mkwrite(pte_mkdirty(orig_dst_pte), dst_vma); > > Indeed, LGTM. > > Reviewed-by: David Hildenbrand Thanks for catching this! Makes total sense to check before modification. Reviewed-by: Suren Baghdasaryan > > -- > Cheers, > > David / dhildenb >