[PATCH wireless v3 1/1] wifi: mac80211: fix mesh fast xmit path deletion UAF

[Zihan Xi]

mesh_fast_tx_cache() stores raw mesh_path pointers. Path deletion
flushes the cache and then frees the path with kfree_rcu(), but a
lookup that already holds the path can insert a new cache entry
after the flush. The cache then points at freed memory.

Set MESH_PATH_DELETED before flushing, and skip inserting a cache
entry if the path or MPP path is already deleted. Check this under
the cache walk lock so it is ordered with the flush. Use WRITE_ONCE()
for the deletion flag updates because the cache check reads flags
without taking state_lock.

Fixes: d5edb9ae8d56 ("wifi: mac80211: mesh fast xmit support")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Vega <vega@xxxxxxxxxx>
Assisted-by: LLM
Co-developed-by: Luxing Yin <root@xxxxxxxxxx>
Signed-off-by: Luxing Yin <root@xxxxxxxxxx>
Signed-off-by: Zihan Xi <zihanx@xxxxxxxxxx>
---
changes in v3:
  - Use WRITE_ONCE() for both deletion-side MESH_PATH_DELETED updates
    to match the lockless READ_ONCE() checks.
  - v2 Link: https://lore.kernel.org/all/cover.1788930567.git.zihanx@xxxxxxxxxx/
changes in v2:
  - Rewrite the commit message.
  - v1 Link: https://lore.kernel.org/all/94174303640c5e1022b31836770bad75f741afbf.1788845030.git.zihanx@xxxxxxxxxx/

 net/mac80211/mesh_pathtbl.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
index 03171cf008557..fa5eac8f0c2ee 100644
--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -577,6 +577,12 @@ void mesh_fast_tx_cache(struct ieee80211_sub_if_data *sdata,
 		goto unlock_sta;
 
 	spin_lock(&cache->walk_lock);
+	if ((READ_ONCE(mpath->flags) & MESH_PATH_DELETED) ||
+	    (mppath && (READ_ONCE(mppath->flags) & MESH_PATH_DELETED))) {
+		kfree(entry);
+		goto unlock_cache;
+	}
+
 	prev = rhashtable_lookup_get_insert_fast(&cache->rht,
 						 &entry->rhash,
 						 fast_tx_rht_params);
@@ -798,7 +804,8 @@ static void mesh_path_free_rcu(struct mesh_table *tbl,
 	struct ieee80211_sub_if_data *sdata = mpath->sdata;
 
 	spin_lock_bh(&mpath->state_lock);
-	mpath->flags |= MESH_PATH_RESOLVING | MESH_PATH_DELETED;
+	WRITE_ONCE(mpath->flags,
+		   mpath->flags | MESH_PATH_RESOLVING | MESH_PATH_DELETED);
 	mesh_gate_del(tbl, mpath);
 	spin_unlock_bh(&mpath->state_lock);
 	timer_shutdown_sync(&mpath->timer);
@@ -812,6 +819,9 @@ static void __mesh_path_del(struct mesh_table *tbl, struct mesh_path *mpath)
 {
 	hlist_del_rcu(&mpath->walk_list);
 	rhashtable_remove_fast(&tbl->rhead, &mpath->rhash, mesh_rht_params);
+	spin_lock_bh(&mpath->state_lock);
+	WRITE_ONCE(mpath->flags, mpath->flags | MESH_PATH_DELETED);
+	spin_unlock_bh(&mpath->state_lock);
 	if (tbl == &mpath->sdata->u.mesh.mpp_paths)
 		mesh_fast_tx_flush_addr(mpath->sdata, mpath->dst);
 	else
-- 
2.43.0