On Sat, Mar 21, 2015 at 03:51:51AM +0200, Konstantin Belousov wrote: > On Sat, Mar 21, 2015 at 02:00:38AM +0100, Mateusz Guzik wrote: > > From: Mateusz Guzik <m...@freebsd.org> > > > > Prior to this change the kernel would take p1's credentials and assign > > them tempororarily to p2. But p1 could change credentials at that time > > and in effect give us a use-after-free. > In which way could it change the credentials ? The assigned credentials > are taken from td_ucred, which, I thought, are guaranteed to be stable > for the duration of a syscall. >
It takes thread's credential in do_fork. But initial copy is taken unlocked from struct proc. Relevant part of the diff: > > @@ -870,7 +867,7 @@ fork1(struct thread *td, int flags, int pages, struct > > proc **procp, > > * XXX: This is ugly; when we copy resource usage, we need to bump > > * per-cred resource counters. > > */ > > - proc_set_cred(newproc, p1->p_ucred); > > + proc_set_cred(newproc, crhold(td->td_ucred)); > > -- Mateusz Guzik <mjguzik gmail.com> _______________________________________________ firstname.lastname@example.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"