Re: [patch 7/8] fdmap v2 - implement sys_socket2

From: Davide Libenzi
Date: Fri Jun 08 2007 - 01:20:34 EST

On Fri, 8 Jun 2007, Eric Dumazet wrote:

> Davide Libenzi a écrit :
> > On Thu, 7 Jun 2007, Eric Dumazet wrote:
> > > I am afraid randomization wont really work if /sbin/init or /bin/bash for
> > > example uses one (or more) unseq fd :
> > > The 'random base' will be propagated at fork()/exec() time ?
> >
> > As I said to Uli, we can't move the base while fds are in there. We can
> > re-randomize it when it's empty. This can also be done (it's a trivial and
> > fast operation - just set fmap->base to a new value) even every time the fd
> > count on the map touches zero.
> >
> Hum, I think it would be better to free fmap if it's empty, instead of change
> fmap->base. (Only in fork() after removal of O_CLOFORK file handles, and in
> exec() after removal of O_CLOEXEC file handles)

That can be done too. When it'll be re-created will be randomized anyway.
I'll probably be doing it everytime fmap->count touches zero in
__put_unused_fd(), so even if the map is not empty at fork and/or exec
time, the program have other chances of randomize in the middle of its

- Davide