linux-kernel - [RFC PATCH 2/5] kprobes: Use helper to parse boolean input from userspace

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Date:   Wed,  9 Jun 2021 19:50:16 +0900
From:   Punit Agrawal <punitagrawal@...il.com>
To:     mhiramat@...nel.org, naveen.n.rao@...ux.ibm.com,
        anil.s.keshavamurthy@...el.com, davem@...emloft.net
Cc:     Punit Agrawal <punitagrawal@...il.com>,
        linux-kernel@...r.kernel.org, guoren@...nel.org,
        linux-csky@...r.kernel.org
Subject: [RFC PATCH 2/5] kprobes: Use helper to parse boolean input from userspace

The "enabled" file provides a debugfs interface to arm / disarm
kprobes in the kernel. In order to parse the buffer containing the
values written from userspace, the callback manually parses the user
input to convert it to a boolean value.

As taking a string value from userspace and converting it to boolean
is a common operation, a helper kstrtobool_from_user() is already
available in the kernel. Update the callback to use the common helper
to parse the write buffer from userspace.

Signed-off-by: Punit Agrawal <punitagrawal@...il.com>
---
 kernel/kprobes.c | 28 ++++++----------------------
 1 file changed, 6 insertions(+), 22 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index fdb1ea2e963b..1a11d3c411bf 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2777,30 +2777,14 @@ static ssize_t read_enabled_file_bool(struct file *file,
 static ssize_t write_enabled_file_bool(struct file *file,
 	       const char __user *user_buf, size_t count, loff_t *ppos)
 {
-	char buf[32];
-	size_t buf_size;
-	int ret = 0;
-
-	buf_size = min(count, (sizeof(buf)-1));
-	if (copy_from_user(buf, user_buf, buf_size))
-		return -EFAULT;
+	bool enable;
+	int ret;
 
-	buf[buf_size] = '\0';
-	switch (buf[0]) {
-	case 'y':
-	case 'Y':
-	case '1':
-		ret = arm_all_kprobes();
-		break;
-	case 'n':
-	case 'N':
-	case '0':
-		ret = disarm_all_kprobes();
-		break;
-	default:
-		return -EINVAL;
-	}
+	ret = kstrtobool_from_user(user_buf, count, &enable);
+	if (ret)
+		return ret;
 
+	ret = enable ? arm_all_kprobes() : disarm_all_kprobes();
 	if (ret)
 		return ret;
 
-- 
2.30.2