Re: [kernel-hardening] Re: [RFC v4 02/18] bpf: Move u64_to_ptr() to BPF headers and inline it

From: David Sterba <dave@jikos.cz>
To: kernel-hardening@lists.openwall.com
Cc: "Mickaël Salaün" <mic@digikod.net>,
	linux-kernel@vger.kernel.org,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Andy Lutomirski" <luto@amacapital.net>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Daniel Mack" <daniel@zonque.org>,
	"David Drysdale" <drysdale@google.com>,
	"David S . Miller" <davem@davemloft.net>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	"James Morris" <james.l.morris@oracle.com>,
	"Jann Horn" <jann@thejh.net>, "Kees Cook" <keescook@chromium.org>,
	"Paul Moore" <pmoore@redhat.com>,
	"Sargun Dhillon" <sargun@sargun.me>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	"Tejun Heo" <tj@kernel.org>, "Thomas Graf" <tgraf@suug.ch>,
	"Will Drewry" <wad@chromium.org>,
	linux-api@vger.kernel.org, linux-security-module@vger.kernel.org,
	netdev@vger.kernel.org, cgroups@vger.kernel.org
Subject: Re: [kernel-hardening] Re: [RFC v4 02/18] bpf: Move u64_to_ptr() to BPF headers and inline it
Date: Wed, 26 Oct 2016 15:52:16 +0200	[thread overview]
Message-ID: <20161026135216.GE15400@twin.jikos.cz> (raw)
In-Reply-To: <4045933.vGduYR3PCp@wuerfel>

On Wed, Oct 26, 2016 at 09:19:08AM +0200, Arnd Bergmann wrote:
> On Wednesday, October 26, 2016 8:56:38 AM CEST Mickaël Salaün wrote:
> >  include/linux/bpf.h  | 6 ++++++
> >  kernel/bpf/syscall.c | 6 ------
> >  2 files changed, 6 insertions(+), 6 deletions(-)
> > 
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index c201017b5730..cf87db6daf27 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -283,6 +283,12 @@ static inline void bpf_long_memcpy(void *dst, const void *src, u32 size)
> >  
> >  /* verify correctness of eBPF program */
> >  int bpf_check(struct bpf_prog **fp, union bpf_attr *attr);
> > +
> > +/* helper to convert user pointers passed inside __aligned_u64 fields */
> > +static inline void __user *u64_to_ptr(__u64 val)
> > +{
> > +       return (void __user *) (unsigned long) val;
> > +}
> >  #else
> > 
> 
> 
> We already have at least six copies of this helper:
> 
> fs/btrfs/qgroup.c:#define u64_to_ptr(x) ((struct btrfs_qgroup *)(uintptr_t)x)

This one does not take __user pointers, unlike the rest. Anyway, the name is
misleading, I'll send a cleanup. Thanks.

> kernel/bpf/syscall.c:static void __user *u64_to_ptr(__u64 val)
> drivers/staging/android/ion/ion_test.c:#define u64_to_uptr(x) ((void __user *)(unsigned long)(x))
> drivers/firewire/core-cdev.c:static void __user *u64_to_uptr(u64 value)
> drivers/staging/android/ion/ion_test.c:#define u64_to_uptr(x) ((void __user *)(unsigned long)(x))
> include/linux/kernel.h:#define u64_to_user_ptr(x) (            \
> 
> Just use the one in linux/kernel.h
> 
> 	Arnd