| Message ID | 20190320020642.4000-26-peterx@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | userfaultfd: write protection support | expand |
On Wed, Mar 20, 2019 at 10:06:39AM +0800, Peter Xu wrote: > In change_pte_range() we do nothing for uffd if the PTE is a swap > entry. That can lead to data mismatch if the page that we are going > to write protect is swapped out when sending the UFFDIO_WRITEPROTECT. > This patch applies/removes the uffd-wp bit even for the swap entries. > > Signed-off-by: Peter Xu <peterx@redhat.com> This one seems to address some of the comments i made on patch 17 not all thought. Maybe squash them together ? > --- > > I kept this patch a standalone one majorly to make review easier. The > patch can be considered as standalone or to squash into the patch > "userfaultfd: wp: support swap and page migration". > --- > mm/mprotect.c | 24 +++++++++++++----------- > 1 file changed, 13 insertions(+), 11 deletions(-) > > diff --git a/mm/mprotect.c b/mm/mprotect.c > index 96c0f521099d..a23e03053787 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -183,11 +183,11 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, > } > ptep_modify_prot_commit(mm, addr, pte, ptent); > pages++; > - } else if (IS_ENABLED(CONFIG_MIGRATION)) { > + } else if (is_swap_pte(oldpte)) { > swp_entry_t entry = pte_to_swp_entry(oldpte); > + pte_t newpte; > > if (is_write_migration_entry(entry)) { > - pte_t newpte; > /* > * A protection check is difficult so > * just be safe and disable write > @@ -198,22 +198,24 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, > newpte = pte_swp_mksoft_dirty(newpte); > if (pte_swp_uffd_wp(oldpte)) > newpte = pte_swp_mkuffd_wp(newpte); > - set_pte_at(mm, addr, pte, newpte); > - > - pages++; > - } > - > - if (is_write_device_private_entry(entry)) { > - pte_t newpte; > - > + } else if (is_write_device_private_entry(entry)) { > /* > * We do not preserve soft-dirtiness. See > * copy_one_pte() for explanation. > */ > make_device_private_entry_read(&entry); > newpte = swp_entry_to_pte(entry); > - set_pte_at(mm, addr, pte, newpte); > + } else { > + newpte = oldpte; > + } > > + if (uffd_wp) > + newpte = pte_swp_mkuffd_wp(newpte); > + else if (uffd_wp_resolve) > + newpte = pte_swp_clear_uffd_wp(newpte); > + > + if (!pte_same(oldpte, newpte)) { > + set_pte_at(mm, addr, pte, newpte); > pages++; > } > } > -- > 2.17.1 >
diff --git a/mm/mprotect.c b/mm/mprotect.c index 96c0f521099d..a23e03053787 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -183,11 +183,11 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, } ptep_modify_prot_commit(mm, addr, pte, ptent); pages++; - } else if (IS_ENABLED(CONFIG_MIGRATION)) { + } else if (is_swap_pte(oldpte)) { swp_entry_t entry = pte_to_swp_entry(oldpte); + pte_t newpte; if (is_write_migration_entry(entry)) { - pte_t newpte; /* * A protection check is difficult so * just be safe and disable write @@ -198,22 +198,24 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, newpte = pte_swp_mksoft_dirty(newpte); if (pte_swp_uffd_wp(oldpte)) newpte = pte_swp_mkuffd_wp(newpte); - set_pte_at(mm, addr, pte, newpte); - - pages++; - } - - if (is_write_device_private_entry(entry)) { - pte_t newpte; - + } else if (is_write_device_private_entry(entry)) { /* * We do not preserve soft-dirtiness. See * copy_one_pte() for explanation. */ make_device_private_entry_read(&entry); newpte = swp_entry_to_pte(entry); - set_pte_at(mm, addr, pte, newpte); + } else { + newpte = oldpte; + } + if (uffd_wp) + newpte = pte_swp_mkuffd_wp(newpte); + else if (uffd_wp_resolve) + newpte = pte_swp_clear_uffd_wp(newpte); + + if (!pte_same(oldpte, newpte)) { + set_pte_at(mm, addr, pte, newpte); pages++; } }
In change_pte_range() we do nothing for uffd if the PTE is a swap entry. That can lead to data mismatch if the page that we are going to write protect is swapped out when sending the UFFDIO_WRITEPROTECT. This patch applies/removes the uffd-wp bit even for the swap entries. Signed-off-by: Peter Xu <peterx@redhat.com> --- I kept this patch a standalone one majorly to make review easier. The patch can be considered as standalone or to squash into the patch "userfaultfd: wp: support swap and page migration". --- mm/mprotect.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-)