wifi: ath10k: Fix connection after GTK rekeying

[ Upstream commit 487e8a8c3421df0af3707e54c7e069f1d89cbda7 ]

It appears that not all hardware/firmware implementations support
group key deletion correctly, which can lead to connection hangs
and deauthentication following GTK rekeying (delete and install).

To avoid this issue, instead of attempting to delete the key using
the special WMI_CIPHER_NONE value, we now replace the key with an
invalid (random) value.

This behavior has been observed with WCN39xx chipsets.

Tested-on: WCN3990 hw1.0 WLAN.HL.3.3.7.c2-00931-QCAHLSWMTPLZ-1
Reported-by: Alexey Klimov <alexey.klimov@linaro.org>
Closes: https://lore.kernel.org/all/DAWJQ2NIKY28.1XOG35E4A682G@linaro.org
Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
Reviewed-by: Baochen Qiang <baochen.qiang@oss.qualcomm.com>
Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>
Tested-by: Alexey Klimov <alexey.klimov@linaro.org> # QRB2210 RB1
Link: https://patch.msgid.link/20250902143225.837487-1-loic.poulain@oss.qualcomm.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[uli: backport to 4.19]
Signed-off-by: Ulrich Hecht <uli@kernel.org>
Reviewed-by: Pavel Machek <pavel@nabladev.com>

Author: Loic Poulain

drivers/net/wireless/ath/ath10k/mac.c

@@ -22,6 +22,7 @@
 #include <net/mac80211.h>
 #include <linux/etherdevice.h>
 #include <linux/acpi.h>
+#include <linux/random.h>
 
 #include "hif.h"
 #include "core.h"
@@ -268,8 +269,15 @@ static int ath10k_send_key(struct ath10k_vif *arvif,
 		key->flags |= IEEE80211_KEY_FLAG_GENERATE_IV;
 
 	if (cmd == DISABLE_KEY) {
-		arg.key_cipher = WMI_CIPHER_NONE;
-		arg.key_data = NULL;
+		if (flags & WMI_KEY_GROUP) {
+			/* Not all hardware handles group-key deletion operation
+			 * correctly. Replace the key with a junk value to invalidate it.
+			 */
+			get_random_bytes(key->key, key->keylen);
+		} else {
+			arg.key_cipher = WMI_CIPHER_NONE;
+			arg.key_data = NULL;
+		}
 	}
 
 	return ath10k_wmi_vdev_install_key(arvif->ar, &arg);