[PATCH 1/2] carl9170: re-fix fortified-memset warning @ 2023-06-23 15:23 Arnd Bergmann 2023-06-23 15:24 ` [PATCH 2/2] mac80211: make ieee80211_tx_info padding explicit Arnd Bergmann ` (2 more replies) 0 siblings, 3 replies; 9+ messages in thread From: Arnd Bergmann @ 2023-06-23 15:23 UTC (permalink / raw) To: Christian Lamparter, Kalle Valo, Kees Cook, Johannes Berg Cc: Arnd Bergmann, linux-wireless, linux-kernel From: Arnd Bergmann 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") Signed-off-by: Arnd Bergmann --- drivers/net/wireless/ath/carl9170/tx.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- 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 k * 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)); if (atomic_read(&ar->tx_total_queued)) ar->tx_schedule = true;