wifi: mac80211: Fix UAF in ieee80211_scan_rx()
ieee80211_scan_rx() tries to access scan_req->flags after a
null check, but a UAF is observed when the scan is completed
and __ieee80211_scan_completed() executes, which then calls
cfg80211_scan_done() leading to the freeing of scan_req.
Since scan_req is rcu_dereference()'d, prevent the racing in
__ieee80211_scan_completed() by ensuring that from mac80211's
POV it is no longer accessed from an RCU read critical section
before we call cfg80211_scan_done().
Cc: stable@vger.kernel.org
Link: https://syzkaller.appspot.com/bug?extid=f9acff9bf08a845f225d
Reported-by: syzbot+f9acff9bf08a845f225d@syzkaller.appspotmail.com
Suggested-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Siddh Raman Pant <code@siddh.me>
Link: https://lore.kernel.org/r/20220819200340.34826-1-code@siddh.me
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index fa8ddf5..c4f2aeb 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -469,16 +469,19 @@ static void __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
scan_req = rcu_dereference_protected(local->scan_req,
lockdep_is_held(&local->mtx));
- if (scan_req != local->int_scan_req) {
- local->scan_info.aborted = aborted;
- cfg80211_scan_done(scan_req, &local->scan_info);
- }
RCU_INIT_POINTER(local->scan_req, NULL);
RCU_INIT_POINTER(local->scan_sdata, NULL);
local->scanning = 0;
local->scan_chandef.chan = NULL;
+ synchronize_rcu();
+
+ if (scan_req != local->int_scan_req) {
+ local->scan_info.aborted = aborted;
+ cfg80211_scan_done(scan_req, &local->scan_info);
+ }
+
/* Set power back to normal operating levels. */
ieee80211_hw_config(local, 0);
