Commit 8b401f9ed244 ("bpf: implement bpf_send_signal() helper")
introduced bpf_send_signal() helper. If the context is nmi,
the sending signal work needs to be deferred to irq_work.
If the signal is invalid, the error will appear in irq_work
and it won't be propagated to user.
This patch did an early check in the helper itself to
notify user invalid signal, as suggested by Daniel.
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
kernel/trace/bpf_trace.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 70029eafc71f..fe73926a07cd 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -600,6 +600,12 @@ BPF_CALL_1(bpf_send_signal, u32, sig)
return -EPERM;
if (in_nmi()) {
+ /* Do an early check on signal validity. Otherwise,
+ * the error is lost in deferred irq_work.
+ */
+ if (unlikely(!valid_signal(sig)))
+ return -EINVAL;
+
work = this_cpu_ptr(&send_signal_work);
if (work->irq_work.flags & IRQ_WORK_BUSY)
return -EBUSY;
--
2.17.1
