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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>
This commit is contained in:
Thomas Gleixner 2017-05-17 10:19:49 +02:00 committed by Steven Rostedt (VMware)
parent b9ef0326c0
commit 30e7d894c1
3 changed files with 9 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/linux/kprobes.h
View File

@ -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,

2
kernel/kprobes.c
View File

@ -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);

5
kernel/trace/trace_kprobe.c
View File

@ -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