linux-kernel - [PATCH] kprobes: Fix kill kprobe which has been marked as gone

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Message-Id: <20200820031933.46025-1-songmuchun@bytedance.com>
Date:   Thu, 20 Aug 2020 11:19:33 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     naveen.n.rao@...ux.ibm.com, anil.s.keshavamurthy@...el.com,
        davem@...emloft.net, mhiramat@...nel.org, songliubraving@...com
Cc:     linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>,
        Chengming Zhou <zhouchengming@...edance.com>
Subject: [PATCH] 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: 0cb2f1372baa ("kprobes: Fix NULL pointer dereference at kprobe_ftrace_handler")
Signed-off-by: Muchun Song <songmuchun@...edance.com>
Co-developed-by: Chengming Zhou <zhouchengming@...edance.com>
Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
---
 kernel/kprobes.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index d36e2b017588..7bac3ea44ff4 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2422,7 +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))) {
@@ -2439,6 +2442,7 @@ static int kprobes_module_callback(struct notifier_block *nb,
 				 */
 				kill_kprobe(p);
 			}
+		}
 	}
 	if (val == MODULE_STATE_GOING)
 		remove_module_kprobe_blacklist(mod);
-- 
2.11.0