linux-kernel - [PATCH] usb: core: fix quirks_param

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Date:   Sun, 05 Jul 2020 23:53:27 +0200
From:   "Kars Mulder" <kerneldev@...smulder.nl>
To:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Cc:     "David Laight" <David.Laight@...LAB.COM>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Kai-Heng Feng" <kai.heng.feng@...onical.com>,
        "Pavel Machek" <pavel@...x.de>,
        "Andy Shevchenko" <andy.shevchenko@...il.com>,
        "Oliver Neukum" <oneukum@...e.com>
Subject: [PATCH] usb: core: fix 
 quirks_param_set() writing to a const pointer

The function quirks_param_set() takes as argument a const char* pointer
to the new value of the usbcore.quirks parameter. It then casts this
pointer to a non-const char* pointer and passes it to the strsep()
function, which overwrites the value.

Fix this by copying the value to a local buffer on the stack and 
letting that buffer be written to by strsep().

Fixes: 027bd6cafd9a ("usb: core: Add "quirks" parameter for usbcore")
Signed-off-by: Kars Mulder <kerneldev@...smulder.nl>

---
 drivers/usb/core/quirks.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/core/quirks.c b/drivers/usb/core/quirks.c
index e0b77674869c..86b1a6739b4e 100644
--- a/drivers/usb/core/quirks.c
+++ b/drivers/usb/core/quirks.c
@@ -12,6 +12,8 @@
 #include <linux/usb/hcd.h>
 #include "usb.h"
 
+#define QUIRKS_PARAM_SIZE 128
+
 struct quirk_entry {
 	u16 vid;
 	u16 pid;
@@ -23,19 +25,21 @@ static DEFINE_MUTEX(quirk_mutex);
 static struct quirk_entry *quirk_list;
 static unsigned int quirk_count;
 
-static char quirks_param[128];
+static char quirks_param[QUIRKS_PARAM_SIZE];
 
-static int quirks_param_set(const char *val, const struct kernel_param *kp)
+static int quirks_param_set(const char *value, const struct kernel_param *kp)
 {
+	char val[QUIRKS_PARAM_SIZE];
 	char *p, *field;
 	u16 vid, pid;
 	u32 flags;
 	size_t i;
 	int err;
 
-	err = param_set_copystring(val, kp);
+	err = param_set_copystring(value, kp);
 	if (err)
 		return err;
+	strscpy(val, value, sizeof(val));
 
 	mutex_lock(&quirk_mutex);
 
-- 
2.27.0