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 c328e4f7dcadb4276bddcfbcc97caa323c48a0a3..d0bdb986f759d94691d2c50db8d2c1646bb9ce74 100644 (file)
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -347,6 +347,9 @@ 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 699c5bc51a9219d664578e4d7978dee94d291c82..74522da4d7cdc22b08dfe3b20b2e2d67970b40fd 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -598,7 +598,7 @@ 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 5f688cc724f00abcd9d09686adc75fb96e4b5b02..49cdda8521656783df298fc6d8d9e70d726b3679 100644 (file)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1511,6 +1511,11 @@ 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