linux-kernel - Re: [kernel-hardening] Re: [RFC v4 02/18] bpf: Move u64_to

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Date:   Wed, 26 Oct 2016 15:52:16 +0200
From:   David Sterba <dave@...os.cz>
To:     kernel-hardening@...ts.openwall.com
Cc:     Mickaël Salaün <mic@...ikod.net>,
        linux-kernel@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        Daniel Mack <daniel@...que.org>,
        David Drysdale <drysdale@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        James Morris <james.l.morris@...cle.com>,
        Jann Horn <jann@...jh.net>, Kees Cook <keescook@...omium.org>,
        Paul Moore <pmoore@...hat.com>,
        Sargun Dhillon <sargun@...gun.me>,
        "Serge E . Hallyn" <serge@...lyn.com>, Tejun Heo <tj@...nel.org>,
        Thomas Graf <tgraf@...g.ch>, Will Drewry <wad@...omium.org>,
        linux-api@...r.kernel.org, linux-security-module@...r.kernel.org,
        netdev@...r.kernel.org, cgroups@...r.kernel.org
Subject: Re: [kernel-hardening] Re: [RFC v4 02/18] bpf: Move u64_to_ptr() to
 BPF headers and inline it

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