linux-kernel - [PATCH] kprobes: avoid the kprobe being re-registered

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Message-ID: <1509019885-58481-1-git-send-email-zhouchengming1@huawei.com>
Date:   Thu, 26 Oct 2017 20:11:25 +0800
From:   Zhou Chengming <zhouchengming1@...wei.com>
To:     <ananth@...ux.vnet.ibm.com>, <anil.s.keshavamurthy@...el.com>,
        <davem@...emloft.net>, <mhiramat@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <zhouchengming1@...wei.com>
Subject: [PATCH] kprobes: avoid the kprobe being re-registered

Old code use check_kprobe_rereg() to check if the kprobe has been
registered already, but check_kprobe_rereg() will release the
kprobe_mutex then, so maybe two paths will pass the check and
register the same kprobe. This patch put the check inside the mutex.

Signed-off-by: Zhou Chengming <zhouchengming1@...wei.com>
---
 kernel/kprobes.c | 23 ++++++-----------------
 1 file changed, 6 insertions(+), 17 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index a1606a4..2a4873a 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1443,19 +1443,6 @@ 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)
-{
-	int ret = 0;
-
-	mutex_lock(&kprobe_mutex);
-	if (__get_valid_kprobe(p))
-		ret = -EINVAL;
-	mutex_unlock(&kprobe_mutex);
-
-	return ret;
-}
-
 int __weak arch_check_ftrace_location(struct kprobe *p)
 {
 	unsigned long ftrace_addr;
@@ -1536,10 +1523,6 @@ int register_kprobe(struct kprobe *p)
 		return PTR_ERR(addr);
 	p->addr = addr;
 
-	ret = check_kprobe_rereg(p);
-	if (ret)
-		return ret;
-
 	/* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
 	p->flags &= KPROBE_FLAG_DISABLED;
 	p->nmissed = 0;
@@ -1551,6 +1534,12 @@ int register_kprobe(struct kprobe *p)
 
 	mutex_lock(&kprobe_mutex);
 
+	/* Return error if the kprobe is being re-registered */
+	if (__get_valid_kprobe(p)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
 	old_p = get_kprobe(p->addr);
 	if (old_p) {
 		/* Since this may unoptimize old_p, locking text_mutex. */
-- 
1.8.3.1