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

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 30f90c1a0aaf923d2227ae5ba5323ea5da728005..541df0b5b81530741586d6eaf382e9d1a425ac06 100644 (file)
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -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,

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 7367e0ec6f8188973a0ee63539cd9a8485e47585..199243bba5543a252fe8ea91a3dcadd0fd8f486c 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -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);
 

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 8485f6738a87cba32a070543b4ae7b8c434ad04c..c129fca6ec993a85aeb30c7e3aa69254e3f5ac16 100644 (file)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -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