On 08/26, Eric W. Biederman wrote:
>
> Oleg Nesterov <oleg@xxxxxxxxxx> writes:
> >
> > And I also assume that you agree with this change ;)
>
> I don't disagree. Comparing tgid to pids is goofy and my brain is
> elsewhere so I have no thought through the implications.
>
> Actually thinking I think the check should really be. In which case we
> are comparing what we really care about.
>
> int proc_fd_permission(struct inode *inode, int mask)
> {
> int rv = generic_permission(inode, mask);
> if (rv == 0)
> return 0;
>
> rcu_read_lock();
> struct task *task = pid_task(proc_pid(inode));
> if (task && (current->files == task->files))
But for what?
To me, this looks like the unnecessary semantic complication. It
looks as if we actually need to restrict the access to /proc/self/fd
or /proc/<tgid>/fd or /proc/<subthread-tid>/fd.
I do not think there is any security reason to deny this. They share
->mm, a sub-thread can do "everything" with its leader or vice versa.
same_thread_group() looks more simple and natural to me. And note
that __ptrace_may_access() was recently changed (in -mm) to use
same_thread_group() instead of "task == current".
So personally I'd prefer to not change this patch and I think it
makes sense even with "make /proc/self point to thread" I sent.
But. please tell me if you really dislike it. You are maintainer,
I won't argue.
Oleg.
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