Commit e1afb702 authored May 25, 2019 by Yonghong Song Committed by Daniel Borkmann May 28, 2019

bpf: check signal validity in nmi for bpf_send_signal() helper



Commit 8b401f9e ("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.

Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

parent 0d97dacc

kernel/trace/bpf_trace.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -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;

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