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From:   Wang ShaoBo <bobo.shaobowang@huawei.com>
CC:     <cj.chengjian@huawei.com>, <huawei.libin@huawei.com>,
        <xiexiuqi@huawei.com>, <bobo.shaobowang@huawei.com>,
        <rostedt@goodmis.org>, <naveen.n.rao@linux.ibm.com>,
        <anil.s.keshavamurthy@intel.com>, <davem@davemloft.net>,
        <linux-kernel@vger.kernel.org>
Subject: [PATCH v2] kretprobe: avoid re-registration of the same kretprobe earlier
Date:   Thu, 28 Jan 2021 20:44:27 +0800
Message-ID: <20210128124427.2031088-1-bobo.shaobowang@huawei.com>
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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 running register_kretprobe()'s body, 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 | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index f7fb5d135930..5c4a884953e9 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1978,6 +1978,10 @@ int register_kretprobe(struct kretprobe *rp)
 	if (!kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, rp->kp.offset))
 		return -EINVAL;
 
+	/* If only rp->kp.addr is specified, check reregistering kprobes */
+	if (rp->kp.addr && check_kprobe_rereg(&rp->kp))
+		return -EINVAL;
+
 	if (kretprobe_blacklist_size) {
 		addr = kprobe_addr(&rp->kp);
 		if (IS_ERR(addr))
-- 
2.25.1