[PATCH] usb: core: fix quirks_param_set() writing to a const pointer

Kars Mulder
2020-07-05T21:53:32Z

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@karsmulder.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