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bpf: Use this_cpu_{inc_return|dec} for prog->active
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: ca06f55b90
("bpf: Add per-program recursion prevention mechanism")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20220901061938.3789460-3-houtao@huaweicloud.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
This commit is contained in:
parent
197827a05e
commit
c89e843a11
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@ -895,7 +895,7 @@ u64 notrace __bpf_prog_enter(struct bpf_prog *prog, struct bpf_tramp_run_ctx *ru
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run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
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if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) {
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if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
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inc_misses_counter(prog);
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return 0;
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}
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@ -930,7 +930,7 @@ void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start, struct bpf_tramp_
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bpf_reset_run_ctx(run_ctx->saved_run_ctx);
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update_prog_stats(prog, start);
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__this_cpu_dec(*(prog->active));
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this_cpu_dec(*(prog->active));
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migrate_enable();
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rcu_read_unlock();
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}
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@ -966,7 +966,7 @@ u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog, struct bpf_tramp_r
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migrate_disable();
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might_fault();
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if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) {
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if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
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inc_misses_counter(prog);
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return 0;
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}
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@ -982,7 +982,7 @@ void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start,
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bpf_reset_run_ctx(run_ctx->saved_run_ctx);
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update_prog_stats(prog, start);
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__this_cpu_dec(*(prog->active));
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this_cpu_dec(*(prog->active));
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migrate_enable();
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rcu_read_unlock_trace();
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}
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