mac80211: mesh: Free ie data when leaving mesh

At ieee80211_join_mesh() some ie data could have been allocated (see
copy_mesh_setup()) and need to be cleaned up when leaving the mesh.

This fixes the following kmemleak report:

unreferenced object 0xffff0000116bc600 (size 128):
  comm "wpa_supplicant", pid 608, jiffies 4294898983 (age 293.484s)
  hex dump (first 32 bytes):
    30 14 01 00 00 0f ac 04 01 00 00 0f ac 04 01 00  0...............
    00 0f ac 08 00 00 00 00 c4 65 40 00 00 00 00 00  .........e@.....
  backtrace:
    [<00000000bebe439d>] __kmalloc_track_caller+0x1c0/0x330
    [<00000000a349dbe1>] kmemdup+0x28/0x50
    [<0000000075d69baa>] ieee80211_join_mesh+0x6c/0x3b8 [mac80211]
    [<00000000683bb98b>] __cfg80211_join_mesh+0x1e8/0x4f0 [cfg80211]
    [<0000000072cb507f>] nl80211_join_mesh+0x520/0x6b8 [cfg80211]
    [<0000000077e9bcf9>] genl_family_rcv_msg+0x374/0x680
    [<00000000b1bd936d>] genl_rcv_msg+0x78/0x108
    [<0000000022c53788>] netlink_rcv_skb+0xb0/0x1c0
    [<0000000011af8ec9>] genl_rcv+0x34/0x48
    [<0000000069e41f53>] netlink_unicast+0x268/0x2e8
    [<00000000a7517316>] netlink_sendmsg+0x320/0x4c0
    [<0000000069cba205>] ____sys_sendmsg+0x354/0x3a0
    [<00000000e06bab0f>] ___sys_sendmsg+0xd8/0x120
    [<0000000037340728>] __sys_sendmsg+0xa4/0xf8
    [<000000004fed9776>] __arm64_sys_sendmsg+0x44/0x58
    [<000000001c1e5647>] el0_svc_handler+0xd0/0x1a0

Fixes: c80d545da3 (mac80211: Let userspace enable and configure vendor specific path selection.)
Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Link: https://lore.kernel.org/r/20200704135007.27292-1-repk@triplefau.lt
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/cfg.c

@@ -2166,6 +2166,7 @@ static int ieee80211_leave_mesh(struct wiphy *wiphy, struct net_device *dev)
 	ieee80211_stop_mesh(sdata);
 	mutex_lock(&sdata->local->mtx);
 	ieee80211_vif_release_channel(sdata);
+	kfree(sdata->u.mesh.ie);
 	mutex_unlock(&sdata->local->mtx);
 
 	return 0;