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... */ .
> 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
