kprobes: fix kill kprobe which has been marked as gone

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@bytedance.com>
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: "Naveen N . Rao" <naveen.n.rao@linux.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Song Liu <songliubraving@fb.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20200822030055.32383-1-songmuchun@bytedance.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 287b263..049da84 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2140,6 +2140,9 @@ 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)) {
                /*
@@ -2419,7 +2422,10 @@ static int kprobes_module_callback(struct notifier_block *nb,
        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))) {
@@ -2436,6 +2442,7 @@ static int kprobes_module_callback(struct notifier_block *nb,
                                 */
                                kill_kprobe(p);
                        }
+               }
        }
        if (val == MODULE_STATE_GOING)
                remove_module_kprobe_blacklist(mod);