From: Siddh Raman Pant <code@xxxxxxxx> commit 60deb9f10eec5c6a20252ed36238b55d8b614a2c upstream. 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@xxxxxxxxxxxxxxx Link: https://syzkaller.appspot.com/bug?extid=f9acff9bf08a845f225d Reported-by: syzbot+f9acff9bf08a845f225d@xxxxxxxxxxxxxxxxxxxxxxxxx Suggested-by: Johannes Berg <johannes@xxxxxxxxxxxxxxxx> Signed-off-by: Siddh Raman Pant <code@xxxxxxxx> Link: https://lore.kernel.org/r/20220819200340.34826-1-code@xxxxxxxx Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/mac80211/scan.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) --- a/net/mac80211/scan.c +++ b/net/mac80211/scan.c @@ -461,16 +461,19 @@ static void __ieee80211_scan_completed(s 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);
