[PATCH 5.4 044/120] wifi: mac80211: Fix UAF in ieee80211_scan_rx()

From: Greg Kroah-Hartman
Date: Mon Sep 26 2022 - 06:40:32 EST


From: Siddh Raman Pant <code@xxxxxxxx>

[ 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@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: Sasha Levin <sashal@xxxxxxxxxx>
---
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 344b2c22e75b..c353162e81ae 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -431,10 +431,6 @@ 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,
@@ -444,6 +440,13 @@ 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);

--
2.35.1