On Wed, Apr 22, 2020 at 05:44:38PM +0200, Florian Weimer wrote:
> * Josh Triplett:
> > This allows the caller of pipe2 to specify one or both file descriptors
> > rather than having them automatically use the lowest available file
> > descriptor. The caller can specify either file descriptor as -1 to
> > allow that file descriptor to use the lowest available.
> >
> > Signed-off-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> > ---
> > fs/pipe.c | 16 ++++++++++++----
> > 1 file changed, 12 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/pipe.c b/fs/pipe.c
> > index 16fb72e9abf7..4681a0d1d587 100644
> > --- a/fs/pipe.c
> > +++ b/fs/pipe.c
> > @@ -936,19 +936,19 @@ static int __do_pipe_flags(int *fd, struct file **files, int flags)
> > int error;
> > int fdw, fdr;
> >
> > - if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
> > + if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT | O_SPECIFIC_FD))
> > return -EINVAL;
> >
> > error = create_pipe_files(files, flags);
> > if (error)
> > return error;
> >
> > - error = get_unused_fd_flags(flags);
> > + error = get_specific_unused_fd_flags(fd[0], flags);
> > if (error < 0)
> > goto err_read_pipe;
> > fdr = error;
> >
> > - error = get_unused_fd_flags(flags);
> > + error = get_specific_unused_fd_flags(fd[1], flags);
> > if (error < 0)
> > goto err_fdr;
> > fdw = error;
> > @@ -969,7 +969,11 @@ static int __do_pipe_flags(int *fd, struct file **files, int flags)
> > int do_pipe_flags(int *fd, int flags)
> > {
> > struct file *files[2];
> > - int error = __do_pipe_flags(fd, files, flags);
> > + int error;
> > +
> > + if (flags & O_SPECIFIC_FD)
> > + return -EINVAL;
> > + error = __do_pipe_flags(fd, files, flags);
> > if (!error) {
> > fd_install(fd[0], files[0]);
> > fd_install(fd[1], files[1]);
> > @@ -987,6 +991,10 @@ static int do_pipe2(int __user *fildes, int flags)
> > int fd[2];
> > int error;
> >
> > + if (flags & O_SPECIFIC_FD)
> > + if (copy_from_user(fd, fildes, sizeof(fd)))
> > + return -EFAULT;
> > +
> > error = __do_pipe_flags(fd, files, flags);
> > if (!error) {
> > if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
>
> Mark, I think this will need (or at least benefit from) some valgrind
> changes.
Yes, this makes pipe2 read the memory of its first argument from
userspace, if and only if its second argument contains the O_SPECIFIC_FD
flag.
- Josh Triplett
