| Message ID | 20190320020642.4000-27-peterx@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | userfaultfd: write protection support | expand |
On Wed, Mar 20, 2019 at 10:06:40AM +0800, Peter Xu wrote: > Only declare _UFFDIO_WRITEPROTECT if the user specified > UFFDIO_REGISTER_MODE_WP and if all the checks passed. Then when the > user registers regions with shmem/hugetlbfs we won't expose the new > ioctl to them. Even with complete anonymous memory range, we'll only > expose the new WP ioctl bit if the register mode has MODE_WP. > > Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: Mike Rapoport <rppt@linux.ibm.com> > --- > fs/userfaultfd.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c > index f1f61a0278c2..7f87e9e4fb9b 100644 > --- a/fs/userfaultfd.c > +++ b/fs/userfaultfd.c > @@ -1456,14 +1456,24 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, > up_write(&mm->mmap_sem); > mmput(mm); > if (!ret) { > + __u64 ioctls_out; > + > + ioctls_out = basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC : > + UFFD_API_RANGE_IOCTLS; > + > + /* > + * Declare the WP ioctl only if the WP mode is > + * specified and all checks passed with the range > + */ > + if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_WP)) > + ioctls_out &= ~((__u64)1 << _UFFDIO_WRITEPROTECT); > + > /* > * Now that we scanned all vmas we can already tell > * userland which ioctls methods are guaranteed to > * succeed on this range. > */ > - if (put_user(basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC : > - UFFD_API_RANGE_IOCTLS, > - &user_uffdio_register->ioctls)) > + if (put_user(ioctls_out, &user_uffdio_register->ioctls)) > ret = -EFAULT; > } > out: > -- > 2.17.1 >
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index f1f61a0278c2..7f87e9e4fb9b 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1456,14 +1456,24 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, up_write(&mm->mmap_sem); mmput(mm); if (!ret) { + __u64 ioctls_out; + + ioctls_out = basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC : + UFFD_API_RANGE_IOCTLS; + + /* + * Declare the WP ioctl only if the WP mode is + * specified and all checks passed with the range + */ + if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_WP)) + ioctls_out &= ~((__u64)1 << _UFFDIO_WRITEPROTECT); + /* * Now that we scanned all vmas we can already tell * userland which ioctls methods are guaranteed to * succeed on this range. */ - if (put_user(basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC : - UFFD_API_RANGE_IOCTLS, - &user_uffdio_register->ioctls)) + if (put_user(ioctls_out, &user_uffdio_register->ioctls)) ret = -EFAULT; } out:
Only declare _UFFDIO_WRITEPROTECT if the user specified UFFDIO_REGISTER_MODE_WP and if all the checks passed. Then when the user registers regions with shmem/hugetlbfs we won't expose the new ioctl to them. Even with complete anonymous memory range, we'll only expose the new WP ioctl bit if the register mode has MODE_WP. Signed-off-by: Peter Xu <peterx@redhat.com> --- fs/userfaultfd.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-)