Re: [PATCH v2 4/8] vfs: add missing checks to copy_file_range

[Amir Goldstein <amir73il@gmail.com>]

On Tue, May 28, 2019 at 7:31 PM Darrick J. Wong <darrick.wong@oracle.com> wrote:
>
> On Tue, May 28, 2019 at 07:26:29PM +0300, Amir Goldstein wrote:
> > On Tue, May 28, 2019 at 7:18 PM Darrick J. Wong <darrick.wong@oracle.com> wrote:
> > >
> > > On Sun, May 26, 2019 at 09:10:55AM +0300, Amir Goldstein wrote:
> > > > Like the clone and dedupe interfaces we've recently fixed, the
> > > > copy_file_range() implementation is missing basic sanity, limits and
> > > > boundary condition tests on the parameters that are passed to it
> > > > from userspace. Create a new "generic_copy_file_checks()" function
> > > > modelled on the generic_remap_checks() function to provide this
> > > > missing functionality.
> > > >
> > > > [Amir] Shorten copy length instead of checking pos_in limits
> > > > because input file size already abides by the limits.
> > > >
> > > > Signed-off-by: Dave Chinner <dchinner@redhat.com>
> > > > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> > > > ---
> > > >  fs/read_write.c    |  3 ++-
> > > >  include/linux/fs.h |  3 +++
> > > >  mm/filemap.c       | 53 ++++++++++++++++++++++++++++++++++++++++++++++
> > > >  3 files changed, 58 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/fs/read_write.c b/fs/read_write.c
> > > > index f1900bdb3127..b0fb1176b628 100644
> > > > --- a/fs/read_write.c
> > > > +++ b/fs/read_write.c
> > > > @@ -1626,7 +1626,8 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
> > > >       if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
> > > >               return -EXDEV;
> > > >
> > > > -     ret = generic_file_rw_checks(file_in, file_out);
> > > > +     ret = generic_copy_file_checks(file_in, pos_in, file_out, pos_out, &len,
> > > > +                                    flags);
> > > >       if (unlikely(ret))
> > > >               return ret;
> > > >
> > > > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > > > index 89b9b73eb581..e4d382c4342a 100644
> > > > --- a/include/linux/fs.h
> > > > +++ b/include/linux/fs.h
> > > > @@ -3050,6 +3050,9 @@ extern int generic_remap_checks(struct file *file_in, loff_t pos_in,
> > > >                               struct file *file_out, loff_t pos_out,
> > > >                               loff_t *count, unsigned int remap_flags);
> > > >  extern int generic_file_rw_checks(struct file *file_in, struct file *file_out);
> > > > +extern int generic_copy_file_checks(struct file *file_in, loff_t pos_in,
> > > > +                                 struct file *file_out, loff_t pos_out,
> > > > +                                 size_t *count, unsigned int flags);
> > > >  extern ssize_t generic_file_read_iter(struct kiocb *, struct iov_iter *);
> > > >  extern ssize_t __generic_file_write_iter(struct kiocb *, struct iov_iter *);
> > > >  extern ssize_t generic_file_write_iter(struct kiocb *, struct iov_iter *);
> > > > diff --git a/mm/filemap.c b/mm/filemap.c
> > > > index 798aac92cd76..1852fbf08eeb 100644
> > > > --- a/mm/filemap.c
> > > > +++ b/mm/filemap.c
> > > > @@ -3064,6 +3064,59 @@ int generic_file_rw_checks(struct file *file_in, struct file *file_out)
> > > >       return 0;
> > > >  }
> > > >
> > > > +/*
> > > > + * Performs necessary checks before doing a file copy
> > > > + *
> > > > + * Can adjust amount of bytes to copy
> > >
> > > That's the @req_count parameter, correct?
> >
> > Correct. Same as generic_remap_checks()
>
> Ok.  Would you mind updating the comment?
>
OK.

Thanks,
Amir.