tracing/kprobes: Enforce kprobes teardown after testing

commit 30e7d894c1478c88d50ce94ddcdbd7f9763d9cdd upstream.

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>
Fixes: 6274de498 ("kprobes: Support delayed unoptimizing")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 8f68490842481286446efc92a835ff38db1f1aac..e23392517db9e9eaecfb9120aa91123f2517e81c 100644 (file)
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -330,7 +330,9 @@ 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,

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index d10ab6b9b5e082e47570ab76b8e5aefa7e58ec5a..695763516908e451ffcabd41f1568d5a0478390e 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -563,7 +563,7 @@ 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);
 

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index c9956440d0e609c51e2032f6f625c4061ba764a4..12ea4ea619eeacc6d679e1f184c4e13b5eed30f7 100644 (file)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1471,6 +1471,11 @@ 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