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

[Eric W. Biederman]

Dave Hansen <haveblue@xxxxxxxxxx> 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
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