[PATCH v3] usb: gadget: g_dnl: Fix NULLPTR dereference

[Michael Ferolito]

The current behaviour of this function will dereference a null pointer
if the serial# environment variable is unset. This was discovered on a
board where U-Boot did not have access to the first 256MB of ram,
resulting in a board crash.
In the event that U-Boot has full access to memory, it will still read
from address 0, which is probably not optimal.
This simple check is enough to fix it

Signed-off-by: Michael Ferolito <michaelsunn101 at gmail.com>
Cc: Marek Vasut <marex at denx.de>
Cc: Heiko Schocher <hs at denx.de>
Cc: Kyungmin Park <kyungmin.park at samsung.com>
---
 drivers/usb/gadget/g_dnl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/g_dnl.c b/drivers/usb/gadget/g_dnl.c
index 631969b340..f2540eb6de 100644
--- a/drivers/usb/gadget/g_dnl.c
+++ b/drivers/usb/gadget/g_dnl.c
@@ -207,7 +207,8 @@ void g_dnl_clear_detach(void)
 static int on_serialno(const char *name, const char *value, enum env_op op,
 		int flags)
 {
-	g_dnl_set_serialnumber((char *)value);
+	if (value)
+		g_dnl_set_serialnumber((char *)value);
 	return 0;
 }
 U_BOOT_ENV_CALLBACK(serialno, on_serialno);
-- 
2.48.1