From: Hou Tao <houtao@huaweicloud.com>
To: bpf@vger.kernel.org
Cc: Song Liu <songliubraving@fb.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Hao Sun <sunhao.th@gmail.com>, Hao Luo <haoluo@google.com>,
Andrii Nakryiko <andrii@kernel.org>, Yonghong Song <yhs@fb.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <kafai@fb.com>, KP Singh <kpsingh@kernel.org>,
"David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Jiri Olsa <jolsa@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
Lorenz Bauer <oss@lmb.io>,
houtao1@huawei.com
Subject: [PATCH bpf-next v2 2/4] bpf: Use this_cpu_{inc_return|dec} for prog->active
Date: Thu, 1 Sep 2022 14:19:36 +0800 [thread overview]
Message-ID: <20220901061938.3789460-3-houtao@huaweicloud.com> (raw)
In-Reply-To: <20220901061938.3789460-1-houtao@huaweicloud.com>
From: Hou Tao <houtao1@huawei.com>
Both __this_cpu_inc_return() and __this_cpu_dec() are not preemption
safe and now migrate_disable() doesn't disable preemption, so the update
of prog-active is not atomic and in theory under fully preemptible kernel
recurisve prevention may do not work.
Fixing by using the preemption-safe and IRQ-safe variants.
Fixes: ca06f55b9002 ("bpf: Add per-program recursion prevention mechanism")
Signed-off-by: Hou Tao <houtao1@huawei.com>
---
kernel/bpf/trampoline.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index ff87e38af8a7..ad76940b02cc 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -895,7 +895,7 @@ u64 notrace __bpf_prog_enter(struct bpf_prog *prog, struct bpf_tramp_run_ctx *ru
run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
- if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) {
+ if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
inc_misses_counter(prog);
return 0;
}
@@ -930,7 +930,7 @@ void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start, struct bpf_tramp_
bpf_reset_run_ctx(run_ctx->saved_run_ctx);
update_prog_stats(prog, start);
- __this_cpu_dec(*(prog->active));
+ this_cpu_dec(*(prog->active));
migrate_enable();
rcu_read_unlock();
}
@@ -966,7 +966,7 @@ u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog, struct bpf_tramp_r
migrate_disable();
might_fault();
- if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) {
+ if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
inc_misses_counter(prog);
return 0;
}
@@ -982,7 +982,7 @@ void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start,
bpf_reset_run_ctx(run_ctx->saved_run_ctx);
update_prog_stats(prog, start);
- __this_cpu_dec(*(prog->active));
+ this_cpu_dec(*(prog->active));
migrate_enable();
rcu_read_unlock_trace();
}
--
2.29.2
next prev parent reply other threads:[~2022-09-01 6:01 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-01 6:19 [PATCH bpf-next v2 0/4] Use this_cpu_xxx for preemption-safety Hou Tao
2022-09-01 6:19 ` [PATCH bpf-next v2 1/4] bpf: Use this_cpu_{inc|dec|inc_return} for bpf_task_storage_busy Hou Tao
2022-09-01 6:19 ` Hou Tao [this message]
2022-09-01 6:19 ` [PATCH bpf-next v2 3/4] selftests/bpf: Move sys_pidfd_open() into task_local_storage_helpers.h Hou Tao
2022-09-01 6:19 ` [PATCH bpf-next v2 4/4] selftests/bpf: Test concurrent updates on bpf_task_storage_busy Hou Tao
2022-09-01 19:37 ` Martin KaFai Lau
2022-09-02 3:16 ` Hou Tao
2022-09-01 19:30 ` [PATCH bpf-next v2 0/4] Use this_cpu_xxx for preemption-safety patchwork-bot+netdevbpf
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