--- /dev/null
+From 6989310f5d4327e8595664954edd40a7f99ddd0d Mon Sep 17 00:00:00 2001
+From: Pi-Hsun Shih <pihsun@chromium.org>
+Date: Wed, 4 Dec 2019 16:13:07 +0800
+Subject: wireless: Use offsetof instead of custom macro.
+
+From: Pi-Hsun Shih <pihsun@chromium.org>
+
+commit 6989310f5d4327e8595664954edd40a7f99ddd0d upstream.
+
+Use offsetof to calculate offset of a field to take advantage of
+compiler built-in version when possible, and avoid UBSAN warning when
+compiling with Clang:
+
+==================================================================
+UBSAN: Undefined behaviour in net/wireless/wext-core.c:525:14
+member access within null pointer of type 'struct iw_point'
+CPU: 3 PID: 165 Comm: kworker/u16:3 Tainted: G S W 4.19.23 #43
+Workqueue: cfg80211 __cfg80211_scan_done [cfg80211]
+Call trace:
+ dump_backtrace+0x0/0x194
+ show_stack+0x20/0x2c
+ __dump_stack+0x20/0x28
+ dump_stack+0x70/0x94
+ ubsan_epilogue+0x14/0x44
+ ubsan_type_mismatch_common+0xf4/0xfc
+ __ubsan_handle_type_mismatch_v1+0x34/0x54
+ wireless_send_event+0x3cc/0x470
+ ___cfg80211_scan_done+0x13c/0x220 [cfg80211]
+ __cfg80211_scan_done+0x28/0x34 [cfg80211]
+ process_one_work+0x170/0x35c
+ worker_thread+0x254/0x380
+ kthread+0x13c/0x158
+ ret_from_fork+0x10/0x18
+===================================================================
+
+Signed-off-by: Pi-Hsun Shih <pihsun@chromium.org>
+Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
+Link: https://lore.kernel.org/r/20191204081307.138765-1-pihsun@chromium.org
+Signed-off-by: Johannes Berg <johannes.berg@intel.com>
+Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ include/uapi/linux/wireless.h | 5 +++--
+ 1 file changed, 3 insertions(+), 2 deletions(-)
+
+--- a/include/uapi/linux/wireless.h
++++ b/include/uapi/linux/wireless.h
+@@ -74,6 +74,8 @@
+ #include <linux/socket.h> /* for "struct sockaddr" et al */
+ #include <linux/if.h> /* for IFNAMSIZ and co... */
+
++#include <stddef.h> /* for offsetof */
++
+ /***************************** VERSION *****************************/
+ /*
+ * This constant is used to know the availability of the wireless
+@@ -1090,8 +1092,7 @@ struct iw_event {
+ /* iw_point events are special. First, the payload (extra data) come at
+ * the end of the event, so they are bigger than IW_EV_POINT_LEN. Second,
+ * we omit the pointer, so start at an offset. */
+-#define IW_EV_POINT_OFF (((char *) &(((struct iw_point *) NULL)->length)) - \
+- (char *) NULL)
++#define IW_EV_POINT_OFF offsetof(struct iw_point, length)
+ #define IW_EV_POINT_LEN (IW_EV_LCP_LEN + sizeof(struct iw_point) - \
+ IW_EV_POINT_OFF)
+