On 3/28/24 2:55 PM, 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]>
Sure... though I think AI-supported compilers will in the future nag about
this again. Oh well!
Acked-by: Christian Lamparter <[email protected]>
> ---
> I found this while testing randconfig builds, a .config that shows this
> for me is at https://pastebin.com/yWFKvZYu
>
> Sorry I failed to follow up to Kees' request for a reproducer when
> I posted this last year.
> ---
> drivers/net/wireless/ath/carl9170/tx.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/ath/carl9170/tx.c b/drivers/net/wireless/ath/carl9170/tx.c
> index e902ca80eba7..0226c31a6cae 100644
> --- a/drivers/net/wireless/ath/carl9170/tx.c
> +++ b/drivers/net/wireless/ath/carl9170/tx.c
> @@ -280,7 +280,8 @@ static void carl9170_tx_release(struct kref *ref)
> * carl9170_tx_fill_rateinfo() has filled the rate information
> * before we get to this point.
> */
> - memset_after(&txinfo->status, 0, rates);
> + memset(&txinfo->pad, 0, sizeof(txinfo->pad));
> + memset(&txinfo->rate_driver_data, 0, sizeof(txinfo->rate_driver_data));