bpf: Use this_cpu_{inc|dec|inc_return} for bpf_task_storage_busy
Now migrate_disable() does not disable preemption and under some
architectures (e.g. arm64) __this_cpu_{inc|dec|inc_return} are neither
preemption-safe nor IRQ-safe, so for fully preemptible kernel concurrent
lookups or updates on the same task local storage and on the same CPU
may make bpf_task_storage_busy be imbalanced, and
bpf_task_storage_trylock() on the specific cpu will always fail.
Fixing it by using this_cpu_{inc|dec|inc_return} when manipulating
bpf_task_storage_busy.
Fixes: bc235cdb423a ("bpf: Prevent deadlock from recursive bpf_task_storage_[get|delete]")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20220901061938.3789460-2-houtao@huaweicloud.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index e9014dc..6f29062 100644
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -26,20 +26,20 @@ static DEFINE_PER_CPU(int, bpf_task_storage_busy);
static void bpf_task_storage_lock(void)
{
migrate_disable();
- __this_cpu_inc(bpf_task_storage_busy);
+ this_cpu_inc(bpf_task_storage_busy);
}
static void bpf_task_storage_unlock(void)
{
- __this_cpu_dec(bpf_task_storage_busy);
+ this_cpu_dec(bpf_task_storage_busy);
migrate_enable();
}
static bool bpf_task_storage_trylock(void)
{
migrate_disable();
- if (unlikely(__this_cpu_inc_return(bpf_task_storage_busy) != 1)) {
- __this_cpu_dec(bpf_task_storage_busy);
+ if (unlikely(this_cpu_inc_return(bpf_task_storage_busy) != 1)) {
+ this_cpu_dec(bpf_task_storage_busy);
migrate_enable();
return false;
}
