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

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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.

Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Yonghong Song 2019-05-25 11:57:53 -07:00 committed by Daniel Borkmann
parent 0d97dacc46
commit e1afb70252
1 changed files with 6 additions and 0 deletions
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6
kernel/trace/bpf_trace.c
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@ -600,6 +600,12 @@ BPF_CALL_1(bpf_send_signal, u32, sig)
return -EPERM; return -EPERM;
if (in_nmi()) { 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); work = this_cpu_ptr(&send_signal_work);
if (work->irq_work.flags & IRQ_WORK_BUSY) if (work->irq_work.flags & IRQ_WORK_BUSY)
return -EBUSY; return -EBUSY;