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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,
        Lorenzo Bianconi <lorenzo.bianconi@redhat.com>,
        Johannes Berg <johannes.berg@intel.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.18 038/168] mac80211: do not convert to A-MSDU if frag/subframe limited
Date:   Mon,  8 Oct 2018 20:30:18 +0200
Message-Id: <20181008175621.496071660@linuxfoundation.org>
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4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>

[ Upstream commit 1eb507903665442360a959136dfa3234c43db085 ]

Do not start to aggregate packets in a A-MSDU frame (converting the
first subframe to A-MSDU, adding the header) if max_tx_fragments or
max_amsdu_subframes limits are already exceeded by it. In particular,
this happens when drivers set the limit to 1 to avoid A-MSDUs at all.

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
[reword commit message to be more precise]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/mac80211/tx.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3208,9 +3208,6 @@ static bool ieee80211_amsdu_aggregate(st
 	if (skb->len + head->len > max_amsdu_len)
 		goto out;
 
-	if (!ieee80211_amsdu_prepare_head(sdata, fast_tx, head))
-		goto out;
-
 	nfrags = 1 + skb_shinfo(skb)->nr_frags;
 	nfrags += 1 + skb_shinfo(head)->nr_frags;
 	frag_tail = &skb_shinfo(head)->frag_list;
@@ -3226,6 +3223,9 @@ static bool ieee80211_amsdu_aggregate(st
 	if (max_frags && nfrags > max_frags)
 		goto out;
 
+	if (!ieee80211_amsdu_prepare_head(sdata, fast_tx, head))
+		goto out;
+
 	/*
 	 * Pad out the previous subframe to a multiple of 4 by adding the
 	 * padding to the next one, that's being added. Note that head->len