Staging: rtl8192u: Check kmalloc return value before use the buffer in ieee80211_softmac.c

Check kmalloc return value before use the buffer.

Signed-off-by: Zhitong Wang <zhitong.wangzt@alibaba-inc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c
index 148424a..e5e583e 100644
--- a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c
+++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c
@@ -1580,6 +1580,8 @@
 		if(*(t++) == MFIE_TYPE_CHALLENGE){
 			*chlen = *(t++);
 			*challenge = (u8*)kmalloc(*chlen, GFP_ATOMIC);
+			if (!*challenge)
+				return -ENOMEM;
 			memcpy(*challenge, t, *chlen);
 		}
 	}