bpf: Fix the irq and nmi check in bpf_sk_storage for tracing usage

The intention of the current check is to avoid using bpf_sk_storage
in irq and nmi.  Jakub pointed out that the current check cannot
do that.  For example, in_serving_softirq() returns true
if the softirq handling is interrupted by hard irq.

Fixes: 8e4597c627fb ("bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP")
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201116200113.2868539-1-kafai@fb.com

diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index 359908a7d3c12fb7cbd5935ac93b9a167be3e3b2..a32037daa933712c95659297281f2c61014e869c 100644 (file)
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -415,7 +415,7 @@ static bool bpf_sk_storage_tracing_allowed(const struct bpf_prog *prog)
 BPF_CALL_4(bpf_sk_storage_get_tracing, struct bpf_map *, map, struct sock *, sk,
           void *, value, u64, flags)
 {
-       if (!in_serving_softirq() && !in_task())
+       if (in_irq() || in_nmi())
                return (unsigned long)NULL;
 
        return (unsigned long)____bpf_sk_storage_get(map, sk, value, flags);
@@ -424,7 +424,7 @@ BPF_CALL_4(bpf_sk_storage_get_tracing, struct bpf_map *, map, struct sock *, sk,
 BPF_CALL_2(bpf_sk_storage_delete_tracing, struct bpf_map *, map,
           struct sock *, sk)
 {
-       if (!in_serving_softirq() && !in_task())
+       if (in_irq() || in_nmi())
                return -EPERM;
 
        return ____bpf_sk_storage_delete(map, sk);