Re: [PATCH -mm 5/7] add user namespace

Eric W. Biederman
2006-07-14T20:08:19Z

Dave Hansen <haveblue@us.ibm.com> writes:

> On Fri, 2006-07-14 at 12:06 -0600, Eric W. Biederman wrote:
>> > On Fri, 2006-07-14 at 11:18 -0600, Eric W. Biederman wrote:
>> >> /proc/<pid>/fd/...
>> >> /proc/<pid>/exe
>> >> /proc/<pid>/cwd
>> >>
>> >> It isn't quite the same as you are actually opening a second
>> >> copy of the file descriptor but the essence is the same.
>> >
>> > Last I checked, those were symlinks and didn't work for things like
>> > deleted files. Am I wrong?
>>
>> Yes. They are not really symlinks.
>>
>> Wanting to have an executable that was deleted after it was done
>> executing. I wrote it to a file. opened it, unlinked it, set close
>> on exec, and the exec'd it with /proc/self/fd/N.
>
> Well, on one hand, it makes checkpoints with deleted files easier ;)
>
> Now that I'm actually looking at the code, isn't
> proc_fd_access_allowed()'s permission just derived from ptrace
> permissions? It doesn't seem to involve uids directly at all!

You still have to actually open the file and from there you get to permission().

Eric