Date: Sat, 21 Mar 2015 02:57:22 +0100 From: Mateusz Guzik <mjguzik@gmail.com> To: Konstantin Belousov <kostikbel@gmail.com> Cc: freebsd-current@freebsd.org, jenkins-admin@freebsd.org, Mateusz Guzik <mjg@freebsd.org> Subject: Re: [PATCH 1/3] fork: assign refed credentials earlier Message-ID: <20150321015722.GC27736@dft-labs.eu> In-Reply-To: <20150321015151.GF2379@kib.kiev.ua> References: <20150320122125.GP2379@kib.kiev.ua> <1426899640-6599-1-git-send-email-mjguzik@gmail.com> <1426899640-6599-2-git-send-email-mjguzik@gmail.com> <20150321015151.GF2379@kib.kiev.ua>
next in thread | previous in thread | raw e-mail | index | archive | help
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 <mjg@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>
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20150321015722.GC27736>