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bpf: Use this_cpu_{inc_return|dec} for prog->active

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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:
Hou Tao 2022-09-01 14:19:36 +08:00 committed by Martin KaFai Lau
parent 197827a05e
commit c89e843a11
1 changed files with 4 additions and 4 deletions
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8
kernel/bpf/trampoline.c
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@ -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();
}