[PATCH] kretprobe: avoid re-registration of the same kretprobe earlier

[Wang ShaoBo <bobo.shaobowang@huawei.com>]

Our system encountered a re-init error when re-registering same kretprobe,
where the kretprobe_instance in rp->free_instances is illegally accessed
after re-init.

Implementation to avoid re-registration has been introduced for kprobe
before, but lags for register_kretprobe(). We must check if kprobe has
been re-registered before re-initializing kretprobe, otherwise it will
destroy the data struct of kretprobe registered, which can lead to memory
leak, system crash, also some unexpected behaviors.

we use check_kprobe_rereg() to check if kprobe has been re-registered
before calling register_kretprobe(), for giving a warning message and
terminate registration process.

Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
---
 kernel/kprobes.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 41fdbb7953c6..7f54a70136f3 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2117,6 +2117,14 @@ int register_kretprobe(struct kretprobe *rp)
 		}
 	}
 
+	/*
+	 * Return error if it's being re-registered,
+	 * also give a warning message to the developer.
+	 */
+	ret = check_kprobe_rereg(&rp->kp);
+	if (WARN_ON(ret))
+		return ret;
+
 	rp->kp.pre_handler = pre_handler_kretprobe;
 	rp->kp.post_handler = NULL;
 	rp->kp.fault_handler = NULL;
-- 
2.17.1