On Thu, Apr 18, 2019 at 3:50 PM Pi-Hsun Shih <[email protected]> wrote: > > 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 <[email protected]>
The warning from clang is spurious, but in another case, we felt that the cleanup was worth it, nevertheless (https://lore.kernel.org/patchwork/patch/1050040/). Reviewed-By: Nicolas Boichat <[email protected]> > --- > include/uapi/linux/wireless.h | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/include/uapi/linux/wireless.h b/include/uapi/linux/wireless.h > index 86eca3208b6b..f259cca5cc2b 100644 > --- a/include/uapi/linux/wireless.h > +++ b/include/uapi/linux/wireless.h > @@ -1090,8 +1090,7 @@ 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) > > -- > 2.21.0.392.gf8f6787159e-goog >
