From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alexei Starovoitov <ast@kernel.org>,
davem@davemloft.net, jakub.kicinski@netronome.com,
netdev@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH bpf-next 1/9] bpf: introduce bpf_spin_lock
Date: Wed, 16 Jan 2019 15:23:06 -0800 [thread overview]
Message-ID: <20190116232304.llq3gpmr2yyrufby@ast-mbp> (raw)
In-Reply-To: <cb773e76-e185-d53b-51f4-b78162d99038@iogearbox.net>
On Wed, Jan 16, 2019 at 11:48:15PM +0100, Daniel Borkmann wrote:
>
> I think if I'm not mistaken there should still be a possibility for causing a
> deadlock, namely if in the middle of the critical section I'm using an LD_ABS
> or LD_IND instruction with oob index such that I cause an implicit return 0
> while lock is held. At least I don't see this being caught, probably also for
> such case a test_verifier snippet would be good.
good catch. My earlier implementation was reusing check_reference_leak()
that is called for both bpf_exit and bpf_ld_abs, but then I realized we cannot
call bpf_exit from callee when lock is held and moved that check before
prepare_func_exit() forgetting about ldabs. argh. Will fix.
> Wouldn't we also need to mark queued spinlock functions as notrace such that
> e.g. from kprobe one cannot attach to these causing a deadlock?
there is recursion check already, so I'm not sure that is necessary, but
will add it since it doesn't hurt and safer indeed.
next prev parent reply other threads:[~2019-01-16 23:23 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-16 5:08 [PATCH bpf-next 0/9] introduce bpf_spin_lock Alexei Starovoitov
2019-01-16 5:08 ` [PATCH bpf-next 1/9] bpf: " Alexei Starovoitov
2019-01-16 22:48 ` Daniel Borkmann
2019-01-16 23:16 ` Daniel Borkmann
2019-01-16 23:30 ` Alexei Starovoitov
2019-01-17 0:21 ` Daniel Borkmann
2019-01-17 1:16 ` Alexei Starovoitov
2019-01-17 11:27 ` Daniel Borkmann
2019-01-18 5:51 ` Alexei Starovoitov
2019-01-16 23:23 ` Alexei Starovoitov [this message]
2019-01-17 0:16 ` Martin Lau
2019-01-17 1:02 ` Alexei Starovoitov
2019-01-16 5:08 ` [PATCH bpf-next 2/9] bpf: add support for bpf_spin_lock to cgroup local storage Alexei Starovoitov
2019-01-16 5:08 ` [PATCH bpf-next 3/9] tools/bpf: sync include/uapi/linux/bpf.h Alexei Starovoitov
2019-01-16 5:08 ` [PATCH bpf-next 4/9] selftests/bpf: add bpf_spin_lock tests Alexei Starovoitov
2019-01-16 5:08 ` [PATCH bpf-next 5/9] selftests/bpf: add bpf_spin_lock C test Alexei Starovoitov
2019-01-16 5:08 ` [PATCH bpf-next 8/9] libbpf: introduce bpf_map_lookup_elem_flags() Alexei Starovoitov
2019-01-16 6:18 ` Yonghong Song
2019-01-16 6:28 ` Alexei Starovoitov
2019-01-16 5:08 ` [PATCH bpf-next 9/9] selftests/bpf: test for BPF_F_LOCK Alexei Starovoitov
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