On Wed, May 06 2020 at 00:38:05 +0300, Pavel Begunkov quoth thus:
> On 06/05/2020 00:10, Clay Harris wrote:
> > On Mon, May 04 2020 at 22:39:35 +0300, Pavel Begunkov quoth thus:
> >
> >> do_splice() is used by io_uring, as will be do_tee(). Move f_mode
> >> checks from sys_{splice,tee}() to do_{splice,tee}(), so they're
> >> enforced for io_uring as well.
> >
> > I'm not seeing any check against splicing a pipe to itself in the
> > io_uring path, although maybe I just missed it. As the comment
> > below says: /* Splicing to self would be fun, but... */ .
>
> io_uring just forwards a request to do_splice(), which do the check at the exact
> place you mentioned. The similar story is with do_tee().
Okay. I'd been thinking that since you were moving the file mode
checks into io_uring that the previous place they were called wasn't
on the path. Evidently, you're just moving the mode checks earlier.
> >
> >> Fixes: 7d67af2c0134 ("io_uring: add splice(2) support")
> >> Reported-by: Jann Horn <jannh@xxxxxxxxxx>
> >> Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
> >> ---
> >> fs/splice.c | 45 ++++++++++++++++++---------------------------
> >> 1 file changed, 18 insertions(+), 27 deletions(-)
> >>
> >> diff --git a/fs/splice.c b/fs/splice.c
> >> index 4735defc46ee..fd0a1e7e5959 100644
> >> --- a/fs/splice.c
> >> +++ b/fs/splice.c
> >> @@ -1118,6 +1118,10 @@ long do_splice(struct file *in, loff_t __user *off_in,
> >> loff_t offset;
> >> long ret;
> >>
> >> + if (unlikely(!(in->f_mode & FMODE_READ) ||
> >> + !(out->f_mode & FMODE_WRITE)))
> >> + return -EBADF;
> >> +
> >> ipipe = get_pipe_info(in);
> >> opipe = get_pipe_info(out);
> >>
> >> @@ -1125,12 +1129,6 @@ long do_splice(struct file *in, loff_t __user *off_in,
> >> if (off_in || off_out)
> >> return -ESPIPE;
> >>
> >> - if (!(in->f_mode & FMODE_READ))
> >> - return -EBADF;
> >> -
> >> - if (!(out->f_mode & FMODE_WRITE))
> >> - return -EBADF;
> >> -
> >> /* Splicing to self would be fun, but... */
> >> if (ipipe == opipe)
> >> return -EINVAL;
> >> @@ -1153,9 +1151,6 @@ long do_splice(struct file *in, loff_t __user *off_in,
> >> offset = out->f_pos;
> >> }
> >>
> >> - if (unlikely(!(out->f_mode & FMODE_WRITE)))
> >> - return -EBADF;
> >> -
> >> if (unlikely(out->f_flags & O_APPEND))
> >> return -EINVAL;
> >>
> >> @@ -1440,15 +1435,11 @@ SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
> >> error = -EBADF;
> >> in = fdget(fd_in);
> >> if (in.file) {
> >> - if (in.file->f_mode & FMODE_READ) {
> >> - out = fdget(fd_out);
> >> - if (out.file) {
> >> - if (out.file->f_mode & FMODE_WRITE)
> >> - error = do_splice(in.file, off_in,
> >> - out.file, off_out,
> >> - len, flags);
> >> - fdput(out);
> >> - }
> >> + out = fdget(fd_out);
> >> + if (out.file) {
> >> + error = do_splice(in.file, off_in, out.file, off_out,
> >> + len, flags);
> >> + fdput(out);
> >> }
> >> fdput(in);
> >> }
> >> @@ -1770,6 +1761,10 @@ static long do_tee(struct file *in, struct file *out, size_t len,
> >> struct pipe_inode_info *opipe = get_pipe_info(out);
> >> int ret = -EINVAL;
> >>
> >> + if (unlikely(!(in->f_mode & FMODE_READ) ||
> >> + !(out->f_mode & FMODE_WRITE)))
> >> + return -EBADF;
> >> +
> >> /*
> >> * Duplicate the contents of ipipe to opipe without actually
> >> * copying the data.
> >> @@ -1795,7 +1790,7 @@ static long do_tee(struct file *in, struct file *out, size_t len,
> >>
> >> SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
> >> {
> >> - struct fd in;
> >> + struct fd in, out;
> >> int error;
> >>
> >> if (unlikely(flags & ~SPLICE_F_ALL))
> >> @@ -1807,14 +1802,10 @@ SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
> >> error = -EBADF;
> >> in = fdget(fdin);
> >> if (in.file) {
> >> - if (in.file->f_mode & FMODE_READ) {
> >> - struct fd out = fdget(fdout);
> >> - if (out.file) {
> >> - if (out.file->f_mode & FMODE_WRITE)
> >> - error = do_tee(in.file, out.file,
> >> - len, flags);
> >> - fdput(out);
> >> - }
> >> + out = fdget(fdout);
> >> + if (out.file) {
> >> + error = do_tee(in.file, out.file, len, flags);
> >> + fdput(out);
> >> }
> >> fdput(in);
> >> }
> >> --
> >> 2.24.0
>
> --
> Pavel Begunkov
