Commit 46df3d20 authored Dec 15, 2017 by Josef Bacik Committed by Daniel Borkmann Dec 17, 2017

trace: reenable preemption if we modify the ip



Things got moved around between the original bpf_override_return patches
and the final version, and now the ftrace kprobe dispatcher assumes if
you modified the ip that you also enabled preemption.  Make a comment of
this and enable preemption, this fixes the lockdep splat that happened
when using this feature.

Fixes: 9802d865 ("bpf: add a bpf_override_function helper")
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

parent 4a29c0db

kernel/trace/trace_kprobe.c

+8 −1

Original line number	Diff line number	Diff line
		@@ -1322,8 +1322,15 @@ static int kprobe_dispatcher(struct kprobe kp, struct pt_regs regs)
		if (tk->tp.flags & TP_FLAG_TRACE)
		kprobe_trace_func(tk, regs);
		#ifdef CONFIG_PERF_EVENTS
		if (tk->tp.flags & TP_FLAG_PROFILE)
		if (tk->tp.flags & TP_FLAG_PROFILE) {
		ret = kprobe_perf_func(tk, regs);
		/*
		* The ftrace kprobe handler leaves it up to us to re-enable
		* preemption here before returning if we've modified the ip.
		*/
		if (ret)
		preempt_enable_no_resched();
		}
		#endif
		return ret;
		}