From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Jann Horn <jannh@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Alexei Starovoitov <ast@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
Daniel Borkmann <daniel@iogearbox.net>,
jakub.kicinski@netronome.com,
Network Development <netdev@vger.kernel.org>,
kernel-team@fb.com, Ingo Molnar <mingo@redhat.com>,
Will Deacon <will.deacon@arm.com>,
Paul McKenney <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH v4 bpf-next 1/9] bpf: introduce bpf_spin_lock
Date: Thu, 24 Jan 2019 18:49:36 -0800 [thread overview]
Message-ID: <20190125024935.j5klaklau5wls5av@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <CAG48ez2_e=1TkO_Swz0rgcRJU0a0+m6WWrDscZwgBjU_sHs2dQ@mail.gmail.com>
On Fri, Jan 25, 2019 at 01:18:04AM +0100, Jann Horn wrote:
> On Fri, Jan 25, 2019 at 12:59 AM Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
> > On Thu, Jan 24, 2019 at 07:01:09PM +0100, Peter Zijlstra wrote:
> > > Thanks for having kernel/locking people on Cc...
> > >
> > > On Wed, Jan 23, 2019 at 08:13:55PM -0800, Alexei Starovoitov wrote:
> > >
> > > > Implementation details:
> > > > - on !SMP bpf_spin_lock() becomes nop
> > >
> > > Because no BPF program is preemptible? I don't see any assertions or
> > > even a comment that says this code is non-preemptible.
> > >
> > > AFAICT some of the BPF_RUN_PROG things are under rcu_read_lock() only,
> > > which is not sufficient.
> >
> > nope. all bpf prog types disable preemption. That is must have for all
> > sorts of things to work properly.
> > If there is a prog type that doing rcu_read_lock only it's a serious bug.
> > About a year or so ago we audited everything specifically to make
> > sure everything disables preemption before calling bpf progs.
> > I'm pretty sure nothing crept in in the mean time.
>
> Hmm? What about
> unix_dgram_sendmsg->sk_filter->sk_filter_trim_cap->bpf_prog_run_save_cb->BPF_PROG_RUN?
> That just holds rcu_read_lock(), as far as I can tell...
Looking into it.
First reaction is per-cpu maps and bpf_get_smp_processor_id/numa_id
will return bogus values for sender attached socket socket filters
in CONFIG_PREEMPT kernels. Receive side is in bh.
Not a security issue, but something we have to fix.
next prev parent reply other threads:[~2019-01-25 2:49 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-24 4:13 [PATCH v4 bpf-next 0/9] introduce bpf_spin_lock Alexei Starovoitov
2019-01-24 4:13 ` [PATCH v4 bpf-next 1/9] bpf: " Alexei Starovoitov
2019-01-24 18:01 ` Peter Zijlstra
2019-01-24 18:56 ` Peter Zijlstra
2019-01-24 23:42 ` Paul E. McKenney
2019-01-25 0:05 ` Alexei Starovoitov
2019-01-25 1:22 ` Paul E. McKenney
2019-01-25 1:46 ` Jann Horn
2019-01-25 2:38 ` Alexei Starovoitov
2019-01-25 4:27 ` Alexei Starovoitov
2019-01-25 4:31 ` Paul E. McKenney
2019-01-25 4:47 ` Alexei Starovoitov
2019-01-25 16:02 ` Paul E. McKenney
2019-01-25 4:11 ` Paul E. McKenney
2019-01-25 16:18 ` Jann Horn
2019-01-25 22:51 ` Paul E. McKenney
2019-01-25 23:44 ` Alexei Starovoitov
2019-01-26 0:43 ` Jann Horn
2019-01-26 0:59 ` Jann Horn
2019-01-24 23:58 ` Alexei Starovoitov
2019-01-25 0:18 ` Jann Horn
2019-01-25 2:49 ` Alexei Starovoitov [this message]
2019-01-25 2:29 ` Eric Dumazet
2019-01-25 2:34 ` Alexei Starovoitov
2019-01-25 2:44 ` Eric Dumazet
2019-01-25 2:57 ` Alexei Starovoitov
2019-01-25 8:38 ` Peter Zijlstra
2019-01-25 9:10 ` Peter Zijlstra
2019-01-25 23:42 ` Alexei Starovoitov
2019-01-28 8:24 ` Peter Zijlstra
2019-01-28 8:31 ` Peter Zijlstra
2019-01-28 8:35 ` Peter Zijlstra
2019-01-28 20:49 ` Alexei Starovoitov
2019-01-28 8:43 ` Peter Zijlstra
2019-01-28 21:37 ` Alexei Starovoitov
2019-01-29 8:59 ` Peter Zijlstra
2019-01-30 2:20 ` Alexei Starovoitov
2019-01-25 9:59 ` Peter Zijlstra
2019-01-25 10:09 ` Peter Zijlstra
2019-01-25 10:23 ` Peter Zijlstra
2019-01-26 0:17 ` bpf memory model. Was: " Alexei Starovoitov
2019-01-28 9:24 ` Peter Zijlstra
2019-01-28 21:56 ` Alexei Starovoitov
2019-01-29 9:16 ` Peter Zijlstra
2019-01-30 2:32 ` Alexei Starovoitov
2019-01-30 8:58 ` Peter Zijlstra
2019-01-30 19:36 ` Alexei Starovoitov
2019-01-30 18:11 ` Will Deacon
2019-01-30 18:36 ` Paul E. McKenney
2019-01-30 19:51 ` Alexei Starovoitov
2019-01-30 21:05 ` Paul E. McKenney
2019-01-30 22:57 ` Alexei Starovoitov
2019-01-31 14:01 ` Paul E. McKenney
2019-01-31 18:47 ` Alexei Starovoitov
2019-02-01 14:05 ` Paul E. McKenney
2019-01-30 19:50 ` Alexei Starovoitov
2019-01-24 4:13 ` [PATCH v4 bpf-next 2/9] bpf: add support for bpf_spin_lock to cgroup local storage Alexei Starovoitov
2019-01-24 4:13 ` [PATCH v4 bpf-next 3/9] tools/bpf: sync include/uapi/linux/bpf.h Alexei Starovoitov
2019-01-24 4:13 ` [PATCH v4 bpf-next 4/9] selftests/bpf: add bpf_spin_lock tests Alexei Starovoitov
2019-01-24 4:13 ` [PATCH v4 bpf-next 5/9] selftests/bpf: add bpf_spin_lock C test Alexei Starovoitov
2019-01-24 4:14 ` [PATCH v4 bpf-next 6/9] bpf: introduce BPF_F_LOCK flag Alexei Starovoitov
2019-01-24 4:14 ` [PATCH v4 bpf-next 7/9] tools/bpf: sync uapi/bpf.h Alexei Starovoitov
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