[PATCH 5.10 66/80] wifi: mac80211: Fix UAF in ieee80211_scan_rx()

Greg Kroah-Hartman
2022-09-06T13:41:52Z

From: Siddh Raman Pant <code@siddh.me>

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@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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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);