Commit Message
Greg KH
Oct. 19, 2022, 8:25 a.m. UTC
From: Hou Tao <houtao1@huawei.com> [ Upstream commit c89e843a11f1075d27684f6b42256213e4592383 ] 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> 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> Signed-off-by: Sasha Levin <sashal@kernel.org> --- 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(); }