wifi: mac80211: fix use-after-free in chanctx code

In ieee80211_vif_use_reserved_context(), when we have an
old context and the new context's replace_state is set to
IEEE80211_CHANCTX_REPLACE_NONE, we free the old context
in ieee80211_vif_use_reserved_reassign(). Therefore, we
cannot check the old_ctx anymore, so we should set it to
NULL after this point.

However, since the new_ctx replace state is clearly not
IEEE80211_CHANCTX_REPLACES_OTHER, we're not going to do
anything else in this function and can just return to
avoid accessing the freed old_ctx.

Cc: stable@vger.kernel.org
Fixes: 5bcae31d9cb1 ("mac80211: implement multi-vif in-place reservations")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220601091926.df419d91b165.I17a9b3894ff0b8323ce2afdb153b101124c821e5@changeid

diff --git a/net/mac80211/chan.c b/net/mac80211/chan.c
index e3452445b363585fdf81990baa2f546e3b9b6da2..d8246e00a10b1dbbf136e4e23f2ad44b518075c2 100644 (file)
--- a/net/mac80211/chan.c
+++ b/net/mac80211/chan.c
@@ -1749,12 +1749,9 @@ int ieee80211_vif_use_reserved_context(struct ieee80211_sub_if_data *sdata)
 
        if (new_ctx->replace_state == IEEE80211_CHANCTX_REPLACE_NONE) {
                if (old_ctx)
-                       err = ieee80211_vif_use_reserved_reassign(sdata);
-               else
-                       err = ieee80211_vif_use_reserved_assign(sdata);
+                       return ieee80211_vif_use_reserved_reassign(sdata);
 
-               if (err)
-                       return err;
+               return ieee80211_vif_use_reserved_assign(sdata);
        }
 
        /*