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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Johannes Berg <johannes.berg@intel.com>,
        Kalle Valo <kvalo@kernel.org>
Subject: [PATCH 4.19 143/287] wifi: mac80211: fix use-after-free in chanctx code
Date:   Mon, 13 Jun 2022 12:09:27 +0200
Message-Id: <20220613094928.212812400@linuxfoundation.org>
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From: Johannes Berg <johannes.berg@intel.com>

commit 2965c4cdf7ad9ce0796fac5e57debb9519ea721e upstream.

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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/mac80211/chan.c |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

--- a/net/mac80211/chan.c
+++ b/net/mac80211/chan.c
@@ -1638,12 +1638,9 @@ int ieee80211_vif_use_reserved_context(s
 
 	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);
 	}
 
 	/*