From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx> If for some reason a function is called that triggers the recursion detection of live patching, trigger a warning. By not executing the live patch code, it is possible that the old unpatched function will be called placing the system into an unknown state. Link: https://lore.kernel.org/r/20201029145709.GD16774@alley Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Cc: Jiri Kosina <jikos@xxxxxxxxxx> Cc: Joe Lawrence <joe.lawrence@xxxxxxxxxx> Cc: live-patching@xxxxxxxxxxxxxxx Suggested-by: Miroslav Benes <mbenes@xxxxxxx> Reviewed-by: Petr Mladek <pmladek@xxxxxxxx> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> --- Changes since v2: - Blame Miroslav instead of Petr ;-) kernel/livepatch/patch.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c index 6c0164d24bbd..15480bf3ce88 100644 --- a/kernel/livepatch/patch.c +++ b/kernel/livepatch/patch.c @@ -50,7 +50,7 @@ static void notrace klp_ftrace_handler(unsigned long ip, ops = container_of(fops, struct klp_ops, fops); bit = ftrace_test_recursion_trylock(); - if (bit < 0) + if (WARN_ON_ONCE(bit < 0)) return; /* * A variant of synchronize_rcu() is used to allow patching functions -- 2.28.0
