Re: [PATCH v2 2/2] fs: avoid fdput() after failed fdget() in kernel_read_file_from_fd()

[Luis Chamberlain <mcgrof@kernel.org>]

On Wed, May 13, 2020 at 06:49:50AM +0100, Al Viro wrote:
> On Tue, May 12, 2020 at 01:43:05PM -0600, Shuah Khan wrote:
> > diff --git a/fs/exec.c b/fs/exec.c
> > index 06b4c550af5d..ea24bdce939d 100644
> > --- a/fs/exec.c
> > +++ b/fs/exec.c
> > @@ -1021,8 +1021,8 @@ int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
> >  		goto out;
> >  
> >  	ret = kernel_read_file(f.file, buf, size, max_size, id);
> > -out:
> >  	fdput(f);
> > +out:
> >  	return ret;
> 
> Incidentally, why is that thing exported?

Both kernel_read_file_from_fd() and kernel_read_file() are exported
because they have users, however kernel_read_file() only has security
stuff as a user. Do we want to get rid of the lsm hook for it?

I also have some non-posted patches which tucks away these kernel_read*()
exports under a symbol namespace, to avoid wide-spread use / abuse on
areas in the kernel, so I'd be happy to take this on if we want to
remove it export / lsm hook as part of my series. I did this as there
is another series of patches for a new driver which extend these family
of functions with a now pread() variant....

  Luis