Commit 30e7d894 authored May 17, 2017 by Thomas Gleixner Committed by Steven Rostedt (VMware) May 17, 2017

tracing/kprobes: Enforce kprobes teardown after testing

Enabling the tracer selftest triggers occasionally the warning in
text_poke(), which warns when the to be modified page is not marked
reserved.

The reason is that the tracer selftest installs kprobes on functions marked
__init for testing. These probes are removed after the tests, but that
removal schedules the delayed kprobes_optimizer work, which will do the
actual text poke. If the work is executed after the init text is freed,
then the warning triggers. The bug can be reproduced reliably when the work
delay is increased.

Flush the optimizer work and wait for the optimizing/unoptimizing lists to
become empty before returning from the kprobes tracer selftest. That
ensures that all operations which were queued due to the probes removal
have completed.

Link: http://lkml.kernel.org/r/20170516094802.76a468bb@gandalf.local.home



Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 6274de49 ("kprobes: Support delayed unoptimizing")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

parent b9ef0326

include/linux/kprobes.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -349,6 +349,9 @@ extern int proc_kprobes_optimization_handler(struct ctl_table *table,
		int write, void __user *buffer,
		size_t length, loff_t ppos);
		#endif
		extern void wait_for_kprobe_optimizer(void);
		#else
		static inline void wait_for_kprobe_optimizer(void) { }
		#endif /* CONFIG_OPTPROBES */
		#ifdef CONFIG_KPROBES_ON_FTRACE
		extern void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,

kernel/kprobes.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -595,7 +595,7 @@ static void kprobe_optimizer(struct work_struct *work)
		}

		/* Wait for completing optimization and unoptimization */
		static void wait_for_kprobe_optimizer(void)
		void wait_for_kprobe_optimizer(void)
		{
		mutex_lock(&kprobe_mutex);

kernel/trace/trace_kprobe.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -1535,6 +1535,11 @@ static __init int kprobe_trace_self_tests_init(void)

		end:
		release_all_trace_kprobes();
		/*
		* Wait for the optimizer work to finish. Otherwise it might fiddle
		* with probes in already freed __init text.
		*/
		wait_for_kprobe_optimizer();
		if (warn)
		pr_cont("NG: Some tests are failed. Please check them.\n");
		else

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