linux-kernel - [PATCH net-next 08/11] ath9k: work around false-positive gcc warning

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Message-Id: <20201026213040.3889546-8-arnd@kernel.org>
Date:   Mon, 26 Oct 2020 22:29:55 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     QCA ath9k Development <ath9k-devel@....qualcomm.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Arnd Bergmann <arnd@...db.de>, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net-next 08/11] ath9k: work around false-positive gcc warning

From: Arnd Bergmann <arnd@...db.de>

gcc-10 shows a false-positive warning with CONFIG_KASAN:

drivers/net/wireless/ath/ath9k/dynack.c: In function 'ath_dynack_sample_tx_ts':
include/linux/etherdevice.h:290:14: warning: writing 4 bytes into a region of size 0 [-Wstringop-overflow=]
  290 |  *(u32 *)dst = *(const u32 *)src;
      |  ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~

Until gcc is fixed, work around this by using memcpy() in place
of ether_addr_copy(). Hopefully gcc-11 will not have this problem.

Link: https://godbolt.org/z/sab1MK
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97490
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/net/wireless/ath/ath9k/dynack.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/wireless/ath/ath9k/dynack.c b/drivers/net/wireless/ath/ath9k/dynack.c
index fbeb4a739d32..e4eb96b26ca4 100644
--- a/drivers/net/wireless/ath/ath9k/dynack.c
+++ b/drivers/net/wireless/ath/ath9k/dynack.c
@@ -247,8 +247,14 @@ void ath_dynack_sample_tx_ts(struct ath_hw *ah, struct sk_buff *skb,
 	ridx = ts->ts_rateindex;
 
 	da->st_rbf.ts[da->st_rbf.t_rb].tstamp = ts->ts_tstamp;
+#if defined(CONFIG_KASAN) && (CONFIG_GCC_VERSION >= 100000) && (CONFIG_GCC_VERSION < 110000)
+	/* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97490 */
+	memcpy(da->st_rbf.addr[da->st_rbf.t_rb].h_dest, hdr->addr1, ETH_ALEN);
+	memcpy(da->st_rbf.addr[da->st_rbf.t_rb].h_src, hdr->addr2, ETH_ALEN);
+#else
 	ether_addr_copy(da->st_rbf.addr[da->st_rbf.t_rb].h_dest, hdr->addr1);
 	ether_addr_copy(da->st_rbf.addr[da->st_rbf.t_rb].h_src, hdr->addr2);
+#endif
 
 	if (!(info->status.rates[ridx].flags & IEEE80211_TX_RC_MCS)) {
 		const struct ieee80211_rate *rate;
-- 
2.27.0