wifi: wfx: fix memory leak when starting AP

Kmemleak reported this error:

    unreferenced object 0xd73d1180 (size 184):
      comm "wpa_supplicant", pid 1559, jiffies 13006305 (age 964.245s)
      hex dump (first 32 bytes):
        00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
        00 00 00 00 00 00 00 00 1e 00 01 00 00 00 00 00  ................
      backtrace:
        [<5ca11420>] kmem_cache_alloc+0x20c/0x5ac
        [<127bdd74>] __alloc_skb+0x144/0x170
        [<fb8a5e38>] __netdev_alloc_skb+0x50/0x180
        [<0f9fa1d5>] __ieee80211_beacon_get+0x290/0x4d4 [mac80211]
        [<7accd02d>] ieee80211_beacon_get_tim+0x54/0x18c [mac80211]
        [<41e25cc3>] wfx_start_ap+0xc8/0x234 [wfx]
        [<93a70356>] ieee80211_start_ap+0x404/0x6b4 [mac80211]
        [<a4a661cd>] nl80211_start_ap+0x76c/0x9e0 [cfg80211]
        [<47bd8b68>] genl_rcv_msg+0x198/0x378
        [<453ef796>] netlink_rcv_skb+0xd0/0x130
        [<6b7c977a>] genl_rcv+0x34/0x44
        [<66b2d04d>] netlink_unicast+0x1b4/0x258
        [<f965b9b6>] netlink_sendmsg+0x1e8/0x428
        [<aadb8231>] ____sys_sendmsg+0x1e0/0x274
        [<d2b5212d>] ___sys_sendmsg+0x80/0xb4
        [<69954f45>] __sys_sendmsg+0x64/0xa8
    unreferenced object 0xce087000 (size 1024):
      comm "wpa_supplicant", pid 1559, jiffies 13006305 (age 964.246s)
      hex dump (first 32 bytes):
        00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
        10 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00  ...@............
      backtrace:
        [<9a993714>] __kmalloc_track_caller+0x230/0x600
        [<f83ea192>] kmalloc_reserve.constprop.0+0x30/0x74
        [<a2c61343>] __alloc_skb+0xa0/0x170
        [<fb8a5e38>] __netdev_alloc_skb+0x50/0x180
        [<0f9fa1d5>] __ieee80211_beacon_get+0x290/0x4d4 [mac80211]
        [<7accd02d>] ieee80211_beacon_get_tim+0x54/0x18c [mac80211]
        [<41e25cc3>] wfx_start_ap+0xc8/0x234 [wfx]
        [<93a70356>] ieee80211_start_ap+0x404/0x6b4 [mac80211]
        [<a4a661cd>] nl80211_start_ap+0x76c/0x9e0 [cfg80211]
        [<47bd8b68>] genl_rcv_msg+0x198/0x378
        [<453ef796>] netlink_rcv_skb+0xd0/0x130
        [<6b7c977a>] genl_rcv+0x34/0x44
        [<66b2d04d>] netlink_unicast+0x1b4/0x258
        [<f965b9b6>] netlink_sendmsg+0x1e8/0x428
        [<aadb8231>] ____sys_sendmsg+0x1e0/0x274
        [<d2b5212d>] ___sys_sendmsg+0x80/0xb4

However, since the kernel is build optimized, it seems the stack is not
accurate. It appears the issue is related to wfx_set_mfp_ap(). The issue
is obvious in this function: memory allocated by ieee80211_beacon_get()
is never released. Fixing this leak makes kmemleak happy.
Reported-by: Ulrich Mohr <u.mohr@semex-engcon.com>
Co-developed-by: Ulrich Mohr <u.mohr@semex-engcon.com>
Signed-off-by: Ulrich Mohr <u.mohr@semex-engcon.com>
Fixes: 268bceec ("staging: wfx: fix BA when device is AP and MFP is enabled")
Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240202164213.1606145-1-jerome.pouiller@silabs.com

drivers/net/wireless/silabs/wfx/sta.c

@@ -344,6 +344,7 @@ static int wfx_set_mfp_ap(struct wfx_vif *wvif)
 	const int pairwise_cipher_suite_count_offset = 8 / sizeof(u16);
 	const int pairwise_cipher_suite_size = 4 / sizeof(u16);
 	const int akm_suite_size = 4 / sizeof(u16);
+	int ret = -EINVAL;
 	const u16 *ptr;
 
 	if (unlikely(!skb))
@@ -352,22 +353,26 @@ static int wfx_set_mfp_ap(struct wfx_vif *wvif)
 	ptr = (u16 *)cfg80211_find_ie(WLAN_EID_RSN, skb->data + ieoffset,
 				      skb->len - ieoffset);
 	if (unlikely(!ptr))
-		return -EINVAL;
+		goto free_skb;
 
 	ptr += pairwise_cipher_suite_count_offset;
 	if (WARN_ON(ptr > (u16 *)skb_tail_pointer(skb)))
-		return -EINVAL;
+		goto free_skb;
 
 	ptr += 1 + pairwise_cipher_suite_size * *ptr;
 	if (WARN_ON(ptr > (u16 *)skb_tail_pointer(skb)))
-		return -EINVAL;
+		goto free_skb;
 
 	ptr += 1 + akm_suite_size * *ptr;
 	if (WARN_ON(ptr > (u16 *)skb_tail_pointer(skb)))
-		return -EINVAL;
+		goto free_skb;
 
 	wfx_hif_set_mfp(wvif, *ptr & BIT(7), *ptr & BIT(6));
-	return 0;
+	ret = 0;
+
+free_skb:
+	dev_kfree_skb(skb);
+	return ret;
 }
 
 int wfx_start_ap(struct ieee80211_hw *hw, struct ieee80211_vif *vif,