[PATCH 5.8 104/118] kprobes: fix kill kprobe which has been marked as gone

[Greg Kroah-Hartman]

From: Muchun Song <songmuchun@xxxxxxxxxxxxx>

commit b0399092ccebd9feef68d4ceb8d6219a8c0caa05 upstream.

If a kprobe is marked as gone, we should not kill it again.  Otherwise, we
can disarm the kprobe more than once.  In that case, the statistics of
kprobe_ftrace_enabled can unbalance which can lead to that kprobe do not
work.

Fixes: e8386a0cb22f ("kprobes: support probing module __exit function")
Co-developed-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: "Naveen N . Rao" <naveen.n.rao@xxxxxxxxxxxxx>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200822030055.32383-1-songmuchun@xxxxxxxxxxxxx
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/kprobes.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2108,6 +2108,9 @@ static void kill_kprobe(struct kprobe *p
 
 	lockdep_assert_held(&kprobe_mutex);
 
+	if (WARN_ON_ONCE(kprobe_gone(p)))
+		return;
+
 	p->flags |= KPROBE_FLAG_GONE;
 	if (kprobe_aggrprobe(p)) {
 		/*
@@ -2365,7 +2368,10 @@ static int kprobes_module_callback(struc
 	mutex_lock(&kprobe_mutex);
 	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
 		head = &kprobe_table[i];
-		hlist_for_each_entry(p, head, hlist)
+		hlist_for_each_entry(p, head, hlist) {
+			if (kprobe_gone(p))
+				continue;
+
 			if (within_module_init((unsigned long)p->addr, mod) ||
 			    (checkcore &&
 			     within_module_core((unsigned long)p->addr, mod))) {
@@ -2382,6 +2388,7 @@ static int kprobes_module_callback(struc
 				 */
 				kill_kprobe(p);
 			}
+		}
 	}
 	if (val == MODULE_STATE_GOING)
 		remove_module_kprobe_blacklist(mod);