linux-kernel - [PATCH] kprobes: Warn if the kprobe is reregistered

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Message-Id: <161236436734.194052.4058506306336814476.stgit@devnote2>
Date:   Wed,  3 Feb 2021 23:59:27 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     "Naveen N . Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Ananth N Mavinakayanahalli <ananth@...ux.ibm.com>,
        Wang ShaoBo <bobo.shaobowang@...wei.com>,
        Cheng Jian <cj.chengjian@...wei.com>,
        linux-kernel@...r.kernel.org, mhiramat@...nel.org
Subject: [PATCH] kprobes: Warn if the kprobe is reregistered

Warn if the kprobe is reregistered, since there must be
a software bug (actively used resource must not be re-registered)
and caller must be fixed.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 kernel/kprobes.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index d5a3eb74a657..dd1d027455c4 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1520,13 +1520,16 @@ static struct kprobe *__get_valid_kprobe(struct kprobe *p)
 	return ap;
 }
 
-/* Return error if the kprobe is being re-registered */
-static inline int check_kprobe_rereg(struct kprobe *p)
+/*
+ * Warn and return error if the kprobe is being re-registered since
+ * there must be a software bug.
+ */
+static inline int warn_kprobe_rereg(struct kprobe *p)
 {
 	int ret = 0;
 
 	mutex_lock(&kprobe_mutex);
-	if (__get_valid_kprobe(p))
+	if (WARN_ON_ONCE(__get_valid_kprobe(p)))
 		ret = -EINVAL;
 	mutex_unlock(&kprobe_mutex);
 
@@ -1614,7 +1617,7 @@ int register_kprobe(struct kprobe *p)
 		return PTR_ERR(addr);
 	p->addr = addr;
 
-	ret = check_kprobe_rereg(p);
+	ret = warn_kprobe_rereg(p);
 	if (ret)
 		return ret;
 
@@ -1995,7 +1998,7 @@ int register_kretprobe(struct kretprobe *rp)
 		return ret;
 
 	/* If only rp->kp.addr is specified, check reregistering kprobes */
-	if (rp->kp.addr && check_kprobe_rereg(&rp->kp))
+	if (rp->kp.addr && warn_kprobe_rereg(&rp->kp))
 		return -EINVAL;
 
 	if (kretprobe_blacklist_size) {