From: Arnd Bergmann <arnd@xxxxxxxx>
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/20230623152443.2296825-1-arnd@xxxxxxxxxx/
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
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));
if (atomic_read(&ar->tx_total_queued))
ar->tx_schedule = true;
--
2.39.2
