Johannes Berg [off-list ref] writes:

On Mon, 2020-11-02 at 18:26 +0200, Kalle Valo wrote:

quoted

Arnd Bergmann [off-list ref] writes:

quoted

From: Arnd Bergmann <arnd@arndb.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@arndb.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

Isn't there a better way to handle this? I really would not want
checking for GCC versions become a common approach in drivers.

I even think that using memcpy() always is better than the ugly ifdef.

If you put memcpy() always somebody will surely go and clean it up to
use ether_addr_copy() soon ...

I can always add a comment and hope that the cleanup people read
comments :) I did that now in the pending branch:

https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git/commit/?h=pending&id=25cfc077bd7a798d1aa527ad2aa9932bb3284376

Does that look ok? I prefer that over the ifdef.

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