On Thu, Mar 28, 2024 at 02:55:04PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <[email protected]>
>
> The carl9170_tx_release() function sometimes triggers a fortified-memset
> warning in my randconfig builds:
>
> In file included from include/linux/string.h:254,
> from drivers/net/wireless/ath/carl9170/tx.c:40:
> In function 'fortify_memset_chk',
> inlined from 'carl9170_tx_release' at drivers/net/wireless/ath/carl9170/tx.c:283:2,
> inlined from 'kref_put' at include/linux/kref.h:65:3,
> inlined from 'carl9170_tx_put_skb' at drivers/net/wireless/ath/carl9170/tx.c:342:9:
> include/linux/fortify-string.h:493:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
> 493 | __write_overflow_field(p_size_field, size);
>
> Kees previously tried to avoid this by using memset_after(), but it seems
> this does not fully address the problem. I noticed that the memset_after()
> here is done on a different part of the union (status) than the original
> cast was from (rate_driver_data), which may confuse the compiler.
>
> Unfortunately, the memset_after() trick does not work on driver_rates[]
> because that is part of an anonymous struct, and I could not get
> struct_group() to do this either. Using two separate memset() calls
> on the two members does address the warning though.
>
> Fixes: fb5f6a0e8063b ("mac80211: Use memset_after() to clear tx status")
> Link: https://lore.kernel.org/lkml/[email protected]/
> Signed-off-by: Arnd Bergmann <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
--
Kees Cook