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    Subject[PATCH 4.19 64/95] mac80211: Fix ieee80211_amsdu_aggregate frag_tail bug
    Date
    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 5c5908127fcb..adeee760ab4c 100644
    --- a/net/mac80211/tx.c
    +++ b/net/mac80211/tx.c
    @@ -3264,6 +3264,14 @@ 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


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