From: Nicolas Boichat <drinkcat@chromium.org>
To: Pi-Hsun Shih <pihsun@chromium.org>
Cc: open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] wireless: Use offsetof instead of custom macro.
Date: Thu, 2 May 2019 15:56:33 +0800 [thread overview]
Message-ID: <CANMq1KCwcVawg6L1hTKXBgBi66EKdHQrvxr_chR9Kv1ifFREnA@mail.gmail.com> (raw)
In-Reply-To: <20190418075016.252988-1-pihsun@chromium.org>
On Thu, Apr 18, 2019 at 3:50 PM Pi-Hsun Shih <pihsun@chromium.org> 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@chromium.org>
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 <drinkcat@chromium.org>
> ---
> 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
>
next prev parent reply other threads:[~2019-05-02 7:56 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-18 7:50 [PATCH] wireless: Use offsetof instead of custom macro Pi-Hsun Shih
2019-05-02 7:56 ` Nicolas Boichat [this message]
2019-11-27 23:39 ` Brian Norris
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