From: Siddh Raman Pant code@siddh.me
[ Upstream commit 60deb9f10eec5c6a20252ed36238b55d8b614a2c ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- net/mac80211/scan.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c index 701adcb9262e..a73c362a0182 100644 --- a/net/mac80211/scan.c +++ b/net/mac80211/scan.c @@ -385,10 +385,6 @@ 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);
scan_sdata = rcu_dereference_protected(local->scan_sdata, @@ -398,6 +394,13 @@ static void __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted) 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);