On Wed, Dec 4, 2019 at 12:13 AM Pi-Hsun Shih <pihsun@xxxxxxxxxxxx> 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 <pihsun@xxxxxxxxxxxx>
> ---
>
> Change since v1:
> * Add #include <stddef.h>
Thanks for following up on the feedback.
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
>
> ---
> include/uapi/linux/wireless.h | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/include/uapi/linux/wireless.h b/include/uapi/linux/wireless.h
> index 86eca3208b6b..a2c006a364e0 100644
> --- 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)
>
>
> base-commit: c5db92909beddadddb705b92d3388ea50b01e1a2
> --
> 2.24.0.393.g34dc348eaf-goog
>
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--
Thanks,
~Nick Desaulniers
