From: Chih-Kang Chang <[email protected]>
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 <[email protected]>
Signed-off-by: Ping-Ke Shih <[email protected]>
---
net/mac80211/tx.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 8509778ff31f..9e0d4fca1c76 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3406,6 +3406,12 @@ static bool ieee80211_amsdu_aggregate(struct ieee80211_sub_if_data *sdata,
head->len += skb->len;
head->data_len += skb->len;
+
+ /* frag_list should be updated after pskb_expand_head() */
+ frag_tail = &skb_shinfo(head)->frag_list;
+ while (*frag_tail)
+ frag_tail = &(*frag_tail)->next;
+
*frag_tail = skb;
out_recalc:
--
2.25.1
On 2021-08-16 10:51, Ping-Ke Shih wrote:
> From: Chih-Kang Chang <[email protected]>
>
> 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.
I think instead of iterating over fragments a second time, we should
move the ieee80211_amsdu_prepare_head call further up.
- Felix
> -----Original Message-----
> From: Felix Fietkau [mailto:[email protected]]
> Sent: Monday, August 16, 2021 8:23 PM
> To: Pkshih; [email protected]
> Cc: [email protected]; Gary Chang
> Subject: Re: [PATCH 1/2] mac80211: Fix ieee80211_amsdu_aggregate frag_tail bug
>
> On 2021-08-16 10:51, Ping-Ke Shih wrote:
> > From: Chih-Kang Chang <[email protected]>
> >
> > 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.
> I think instead of iterating over fragments a second time, we should
> move the ieee80211_amsdu_prepare_head call further up.
>
The first iteration is used to calculate 'n' and 'nfrags' to decide if
we need to do AMSDU as well as ieee80211_amsdu_prepare_head(), so we
don't have a good idea to move the function upward. However, we have
an alternative idea [1] to fix frag_tail.
[1] https://lore.kernel.org/linux-wireless/[email protected]/T/#u
--
Ping-Ke