Re: [PATCHv10 man-pages 5/5] execveat.2: initial man page for execveat(2)

[Eric W. Biederman]

Rich Felker <dalias@xxxxxxxxxx> writes:

> On Sat, Jan 10, 2015 at 04:14:57AM +0000, Al Viro wrote:

>> Except that if your interpreter does stat(2) (or access(2), or getxattr(2),
>> etc.) before bothering with open(2), you'll get screwed.
>
> Yes, but I think that would be very bad interpreter design.
> stat/getxattr/access/whatever followed by open is always a TOCTOU
> race. The correct sequence of actions is always open followed by
> fstat/fgetxattr/...

Sigh.  I think everyone who has looked at this has been blind.

If userspace is reasonable all we have to do is fix /proc/self/exe
for shell scripts to point at the actual script,
and then pass /proc/self/exe on the shell scripts command line.

At a practical level we have to worry about backwards compability and
chroot jails.  But the existence of a clean implementation with
/proc/self/exe serves a proof of concept that it would not be too
difficult.  When someone cares enough to implement it.

Eric
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