[PATCH bpf-next] bpf: check signal validity in nmi for bpf_send_signal() helper
From: Yonghong Song <hidden>
Date: 2019-05-25 18:57:59
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [security & lsm] (security audit and enforcement using bpf), bpf [tracing], the rest, tracing · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, KP Singh, Matt Bobrowski, Song Liu, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
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 <redacted>
---
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