Arnd Bergmann <a...@kernel.org> writes:

> From: Arnd Bergmann <a...@arndb.de>
>
> gcc-10 shows a false-positive warning with CONFIG_KASAN:
>
> drivers/net/wireless/ath/ath9k/dynack.c: In function 
> 'ath_dynack_sample_tx_ts':
> include/linux/etherdevice.h:290:14: warning: writing 4 bytes into a region of 
> size 0 [-Wstringop-overflow=]
>   290 |  *(u32 *)dst = *(const u32 *)src;
>       |  ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
>
> Until gcc is fixed, work around this by using memcpy() in place
> of ether_addr_copy(). Hopefully gcc-11 will not have this problem.
>
> Link: https://godbolt.org/z/sab1MK
> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97490
> Signed-off-by: Arnd Bergmann <a...@arndb.de>
> ---
>  drivers/net/wireless/ath/ath9k/dynack.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/net/wireless/ath/ath9k/dynack.c 
> b/drivers/net/wireless/ath/ath9k/dynack.c
> index fbeb4a739d32..e4eb96b26ca4 100644
> --- a/drivers/net/wireless/ath/ath9k/dynack.c
> +++ b/drivers/net/wireless/ath/ath9k/dynack.c
> @@ -247,8 +247,14 @@ void ath_dynack_sample_tx_ts(struct ath_hw *ah, struct 
> sk_buff *skb,
>       ridx = ts->ts_rateindex;
>  
>       da->st_rbf.ts[da->st_rbf.t_rb].tstamp = ts->ts_tstamp;
> +#if defined(CONFIG_KASAN) && (CONFIG_GCC_VERSION >= 100000) && 
> (CONFIG_GCC_VERSION < 110000)
> +     /* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97490 */
> +     memcpy(da->st_rbf.addr[da->st_rbf.t_rb].h_dest, hdr->addr1, ETH_ALEN);
> +     memcpy(da->st_rbf.addr[da->st_rbf.t_rb].h_src, hdr->addr2, ETH_ALEN);
> +#else
>       ether_addr_copy(da->st_rbf.addr[da->st_rbf.t_rb].h_dest, hdr->addr1);
>       ether_addr_copy(da->st_rbf.addr[da->st_rbf.t_rb].h_src, hdr->addr2);
> +#endif

Isn't there a better way to handle this? I really would not want
checking for GCC versions become a common approach in drivers.

I even think that using memcpy() always is better than the ugly ifdef.

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