Re: [bug report] fanotify: fix copy_event_to_user() fid error clean up

[Dan Carpenter <dan.carpenter@oracle.com>]

On Thu, Jul 22, 2021 at 12:01:41PM +0300, Amir Goldstein wrote:
> On Thu, Jul 22, 2021 at 1:39 AM Matthew Bobrowski <repnop@google.com> wrote:
> > To make things clearer, avoid any future confusion and possibly tripping
> > over such a bug, perhaps it'd be better to split up the fput(f) call into a
> > separate branch outside of the current conditional, simply i.e.
> >
> > ...
> >
> > if (f)
> >         fput(f);
> >
> > ...
> >
> > Thoughts?
> 
> smatch (apparently) does not know about the relation that f is non NULL
> if (fd ==  FAN_NOFD) it needs to study create_fd() for that.
> 
> I suggest to move fd_install(fd, f); right after checking of return value
> from create_fd() and without the if (f) condition.
> That should make it clear for human and robots reading this function
> that the cleanup in out_close_fd label is correct.

Yeah.  I got "f" and "fd" mixed up in my head when I was reviewing this
code.  My bad.

Smatch is *supposed* to know about the relationship between those two.
The bug is actually that Smatch records in the database that create_fd()
always fails.  It's a serious bug, and I'm trying to investigate what's
going on and I'm sure that I will fix this before the end of the week.

No need to change the code just to work around a static checker bug.

regards,
dan carpenter