wifi: mac80211: fix RCU use in TDLS fast-xmit

[ Upstream commit 9480adfe4e0f0319b9da04b44e4eebd5ad07e0cd ]

This looks up the link under RCU protection, but isn't
guaranteed to actually have protection. Fix that.

Fixes: 8cc07265b691 ("wifi: mac80211: handle TDLS data frames with MLO")
Link: https://msgid.link/20240129155348.8a9c0b1e1d89.I553f96ce953bb41b0b877d592056164dec20d01c@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index d45d4be..5481acb 100644 (file)
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3086,10 +3086,11 @@ void ieee80211_check_fast_xmit(struct sta_info *sta)
                        /* DA SA BSSID */
                        build.da_offs = offsetof(struct ieee80211_hdr, addr1);
                        build.sa_offs = offsetof(struct ieee80211_hdr, addr2);
+                       rcu_read_lock();
                        link = rcu_dereference(sdata->link[tdls_link_id]);
-                       if (WARN_ON_ONCE(!link))
-                               break;
-                       memcpy(hdr->addr3, link->u.mgd.bssid, ETH_ALEN);
+                       if (!WARN_ON_ONCE(!link))
+                               memcpy(hdr->addr3, link->u.mgd.bssid, ETH_ALEN);
+                       rcu_read_unlock();
                        build.hdr_len = 24;
                        break;
                }