mac80211: Fix ieee80211_amsdu_aggregate frag_tail bug

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: 997eb7fcb902 ("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>

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 2d1193ed3eb524219bd1df328db6531e2ac0d419..824bed71be1382dcc15cb22f8fd1b6eb13e709ae 100644 (file)
--- 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