[PATCH 5.14 089/172] mac80211: Fix ieee80211_amsdu_aggregate frag_tail bug

Greg Kroah-Hartman
2021-10-04T13:34:57Z

From: Chih-Kang Chang <gary.chang@realtek.com>

[ Upstream commit fe94bac626d9c1c5bc98ab32707be8a9d7f8adba ]

In ieee80211_amsdu_aggregate() set a pointer frag_tail point to the
end of skb_shinfo(head)->frag_list, and use it to bind other skb in
the end of this function. But when execute ieee80211_amsdu_aggregate()
->ieee80211_amsdu_realloc_pad()->pskb_expand_head(), the address of
skb_shinfo(head)->frag_list will be changed. However, the
ieee80211_amsdu_aggregate() not update frag_tail after call
pskb_expand_head(). That will cause the second skb can't bind to the
head skb appropriately.So we update the address of frag_tail to fix it.

Fixes: 6e0456b54545 ("mac80211: add A-MSDU tx support")
Signed-off-by: Chih-Kang Chang <gary.chang@realtek.com>
Signed-off-by: Zong-Zhe Yang <kevin_yang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://lore.kernel.org/r/20210830073240.12736-1-pkshih@realtek.com
[reword comment]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/mac80211/tx.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index fa09a369214d..0208f68af394 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3380,6 +3380,14 @@ static bool ieee80211_amsdu_aggregate(struct ieee80211_sub_if_data *sdata,
if (!ieee80211_amsdu_prepare_head(sdata, fast_tx, head))
goto out;

+ /* If n == 2, the "while (*frag_tail)" loop above didn't execute
+ * and frag_tail should be &skb_shinfo(head)->frag_list.
+ * However, ieee80211_amsdu_prepare_head() can reallocate it.
+ * Reload frag_tail to have it pointing to the correct place.
+ */
+ if (n == 2)
+ frag_tail = &skb_shinfo(head)->frag_list;
+
/*
* 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
--
2.33.0