[PATCH 4.17 142/324] mac80211: disable BHs/preemption in ieee80211_tx_control_port()

[Greg Kroah-Hartman]

4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Denis Kenzior <denkenz@xxxxxxxxx>

[ Upstream commit e7441c9274a6a5453e06f4c2b8b5f72eca0a3f17 ]

On pre-emption enabled kernels the following print was being seen due to
missing local_bh_disable/local_bh_enable calls.  mac80211 assumes that
pre-emption is disabled in the data path.

    BUG: using smp_processor_id() in preemptible [00000000] code: iwd/517
    caller is __ieee80211_subif_start_xmit+0x144/0x210 [mac80211]
    [...]
    Call Trace:
    dump_stack+0x5c/0x80
    check_preemption_disabled.cold.0+0x46/0x51
    __ieee80211_subif_start_xmit+0x144/0x210 [mac80211]

Fixes: 911806491425 ("mac80211: Add support for tx_control_port")
Signed-off-by: Denis Kenzior <denkenz@xxxxxxxxx>
[commit message rewrite, fixes tag]
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/mac80211/tx.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -4800,7 +4800,9 @@ int ieee80211_tx_control_port(struct wip
 	skb_reset_network_header(skb);
 	skb_reset_mac_header(skb);
 
+	local_bh_disable();
 	__ieee80211_subif_start_xmit(skb, skb->dev, flags);
+	local_bh_enable();
 
 	return 0;
 }