On Sat, Jan 10, 2015 at 04:27:23PM -0600, Eric W. Biederman wrote: > 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. Is /proc/self/exe a "magic symlink" that's bound to the inode, or just a regular symlink? In the latter case it defeats the whole purpose of using O_EXEC fds and fexecve rather than pathnames. Rich -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
