Re: + syscalls-x86-add-__nr_kcmp-syscall-v8.patch added to -mm tree

[Cyrill Gorcunov <gorcunov@openvz.org>]

On Wed, Feb 15, 2012 at 03:36:06PM +0100, Oleg Nesterov wrote:
> 
> task->files can be NULL, we can race with exit_files().

So I need to call get_files_struct. Thanks Oleg!

> 
> > +	fdt = files_fdtable(task->files);
> > +	if (idx < fdt->max_fds)
> > +		file = fdt->fd[idx];
> 
> You can probably rely on rcu instead of ->file_lock, but this is minor.
> 

I think so. I'll be updating the patch anyway (on top of current
one) so I'll address this comment too. Thanks!

> > +
> > +	/*
> > +	 * One should have enough rights to inspect task details.
> > +	 */
> > +	if (!ptrace_may_access(task1, PTRACE_MODE_READ) ||
> > +	    !ptrace_may_access(task2, PTRACE_MODE_READ)) {
> > +		ret = -EACCES;
> 
> Well, probably this is fine... but may be you can add a comment.
> The task can change its credentials right after ptrace_may_access()
> succeeds. This _looks_ wrong, perhaps it makes sense to  add the
> "we do not care" note.
> 

Wait, how it's differ from other ptrace_may_access calls all over
the kernel? I suppose I'm missing something obvious?

	Cyrill