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From: Arnd Bergmann <>
To: Kees Cook <>,
	Christian Lamparter <>,
	Kalle Valo <>,
	Johannes Berg <>
	"Toke Høiland-Jørgensen" <>,, "Arnd Bergmann" <>,
	"Colin Ian King" <>,
Subject: [PATCH 1/2] [RESEND] wifi: carl9170: re-fix fortified-memset warning
Date: Thu, 28 Mar 2024 14:55:04 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

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 <>
I found this while testing randconfig builds, a .config that shows this
for me is at

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;

  reply	other threads:[~2024-03-28 13:55 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-28 13:55 [PATCH 0/2] wifi: ath: false-positive fortified-memset warnings Arnd Bergmann
2024-03-28 13:55 ` Arnd Bergmann [this message]
2024-03-28 21:51   ` [PATCH 1/2] [RESEND] wifi: carl9170: re-fix fortified-memset warning Kees Cook
2024-03-29 12:56   ` Christian Lamparter
2024-04-04 10:10   ` Kalle Valo
2024-03-28 13:55 ` [PATCH 2/2] wifi: ath9k: work around memset overflow warning Arnd Bergmann
2024-03-28 21:14   ` Toke Høiland-Jørgensen
2024-03-28 21:50   ` Kees Cook

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