From: Steven Rostedt (VMware) <[email protected]> Thomas discovered a bug where the kprobe trace tests had a race condition where the kprobe_optimizer called from a delayed work queue that does the optimizing and "unoptimizing" of a kprobe, can try to modify the text after it has been freed by the init code.
The kprobe trace selftest is a special case, and Thomas and myself investigated to see if there's a chance that this could also be a bug with module unloading, as the code is not obvious to how it handles this. After adding lots of printks, I figured it out. Thomas suggested that this should be commented so that others will not have to go through this exercise again. Suggested-by: Thomas Gleixner <[email protected]> Signed-off-by: Steven Rostedt (VMware) <[email protected]> --- diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 7367e0e..ac386f6 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -2183,6 +2183,12 @@ static int kprobes_module_callback(struct notifier_block *nb, * The vaddr this probe is installed will soon * be vfreed buy not synced to disk. Hence, * disarming the breakpoint isn't needed. + * + * Note, this will also move any optimized probes + * that are pending to be removed from their + * corresponding lists to the freeing_list and + * will not be touched by the delayed + * kprobe_optimizer work handler. */ kill_kprobe(p); }
