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

[Shuah Khan]

On 5/12/20 11:49 PM, Al Viro wrote:
> On Tue, May 12, 2020 at 01:43:05PM -0600, Shuah Khan wrote:
> > Fix kernel_read_file_from_fd() to avoid fdput() after a failed fdget().
> > fdput() doesn't do fput() on this file since FDPUT_FPUT isn't set
> > in fd.flags. Fix it anyway since failed fdget() doesn't require
> > a fdput().
> >
> > This was introduced in a commit that added kernel_read_file_from_fd() as
> > a wrapper for the VFS common kernel_read_file().
> >
> > Fixes: b844f0ecbc56 ("vfs: define kernel_copy_file_from_fd()")
> > Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
> > ---
> >   fs/exec.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > 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;
>
> Again, that goto is a pointless obfuscation; just return -EBADF
> and be done with that.

My reasoning is if this routine ends up growing it might be useful
to handle the return this way.

In any case, I will send v3 for both of these patches.

thanks,
-- Shuah