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Thu, 09 Apr 2026 13:10:03 -0700 (PDT) MIME-Version: 1.0 References: <20260409152822.1073083-1-gourry@gourry.net> In-Reply-To: <20260409152822.1073083-1-gourry@gourry.net> From: Suren Baghdasaryan Date: Thu, 9 Apr 2026 13:09:52 -0700 X-Gm-Features: AQROBzB0iy5dDbU7EKphm65HVhCwBsaWZDeae_72XosBjnydaerQSoGW-5lujDA Message-ID: Subject: Re: [PATCH] userfaultfd: preserve write protection across UFFDIO_MOVE To: Gregory Price Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, rppt@kernel.org, peterx@redhat.com, aarcange@redhat.com, stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 3CF9440014 X-Stat-Signature: aonsr5sgt69qrpm4a3rygj7jdbttyf99 X-Rspam-User: X-HE-Tag: 1775765405-73560 X-HE-Meta: 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 j3lnoWC+ CYP13menH+/grh5OWpseluOeypyn4j5YeFFr+I/aDT539jJxBhAE96NpIokiiawgys8M8E2U7mk6KcrjSnUZhlMLW3c2QkmkI73doeHiiuDGwbB2SNC75zydrn3eiG0IMoC8POcGk0bNcxehxqmfJvYzIOwmqTHfBJ/nMJoG4enrw5LtrGIhD3TdXWqKnlFab4++YOsSLeYA+MbfkH1T2OVIsdKjIEreV0PXxNqczHodpQ0846T5hv7iGRW8Hr/w4MvDgq42nNMS9NoUqR6J8xawLI31UTFSSseqbMduhMoxWChJ9wDHkgNbJYYIdhC6Nj8qxioW+jjxP9+z1QrGJfCIJpJZZDTPfo7N6sszPBFuYEKFWuonoKwbRJVhS5vFo1b3/ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Apr 9, 2026 at 8:28=E2=80=AFAM Gregory Price wr= ote: > > move_present_ptes() unconditionally makes the destination PTE writable, > dropping uffd-wp write-protection from the source PTE. > > The original intent was to follow mremap() behavior, but mremap()'s > move_ptes() preserves the source write state unconditionally. > > Modify uffd to preserve the source write state and check the uffd-wp > condition of the source before setting writable on the destination. > > Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI") > Cc: stable@vger.kernel.org > Signed-off-by: Gregory Price Reviewed-by: Suren Baghdasaryan > --- > mm/userfaultfd.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c > index e6dfd5f28acd..783ca68aed88 100644 > --- a/mm/userfaultfd.c > +++ b/mm/userfaultfd.c > @@ -1123,7 +1123,10 @@ static long move_present_ptes(struct mm_struct *mm= , > orig_dst_pte =3D pte_mksoft_dirty(orig_dst_pte); > if (pte_dirty(orig_src_pte)) > orig_dst_pte =3D pte_mkdirty(orig_dst_pte); > - orig_dst_pte =3D pte_mkwrite(orig_dst_pte, dst_vma); > + if (pte_write(orig_src_pte)) > + orig_dst_pte =3D pte_mkwrite(orig_dst_pte, dst_vm= a); > + if (pte_uffd_wp(orig_src_pte)) > + orig_dst_pte =3D pte_mkuffd_wp(orig_dst_pte); > set_pte_at(mm, dst_addr, dst_pte, orig_dst_pte); > > src_addr +=3D PAGE_SIZE; > -- > 2.52.0 >