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From: Sara Sharon <sara.sharon@intel.com>
Date: Wed, 29 Aug 2018 08:57:02 +0200
Subject: [PATCH] mac80211: avoid kernel panic when building AMSDU from
non-linear SKB
When building building AMSDU from non-linear SKB, we hit a
kernel panic when trying to push the padding to the tail.
Instead, put the padding at the head of the next subframe.
This also fixes the A-MSDU subframes to not have the padding
accounted in the length field and not have pad at all for
the last subframe, both required by the spec.
Fixes: 6e0456b54545 ("mac80211: add A-MSDU tx support")
Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Reviewed-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3064,27 +3064,18 @@ void ieee80211_clear_fast_xmit(struct st
}
static bool ieee80211_amsdu_realloc_pad(struct ieee80211_local *local,
- struct sk_buff *skb, int headroom,
- int *subframe_len)
+ struct sk_buff *skb, int headroom)
{
- int amsdu_len = *subframe_len + sizeof(struct ethhdr);
- int padding = (4 - amsdu_len) & 3;
-
- if (skb_headroom(skb) < headroom || skb_tailroom(skb) < padding) {
+ if (skb_headroom(skb) < headroom) {
I802_DEBUG_INC(local->tx_expand_skb_head);
- if (pskb_expand_head(skb, headroom, padding, GFP_ATOMIC)) {
+ if (pskb_expand_head(skb, headroom, 0, GFP_ATOMIC)) {
wiphy_debug(local->hw.wiphy,
"failed to reallocate TX buffer\n");
return false;
}
}
- if (padding) {
- *subframe_len += padding;
- skb_put_zero(skb, padding);
- }
-
return true;
}
@@ -3108,8 +3099,7 @@ static bool ieee80211_amsdu_prepare_head
if (info->control.flags & IEEE80211_TX_CTRL_AMSDU)
return true;
- if (!ieee80211_amsdu_realloc_pad(local, skb, sizeof(*amsdu_hdr),
- &subframe_len))
+ if (!ieee80211_amsdu_realloc_pad(local, skb, sizeof(*amsdu_hdr)))
return false;
data = skb_push(skb, sizeof(*amsdu_hdr));
@@ -3176,7 +3166,8 @@ static bool ieee80211_amsdu_aggregate(st
void *data;
bool ret = false;
unsigned int orig_len;
- int n = 1, nfrags;
+ int n = 1, nfrags, pad = 0;
+ u16 hdrlen;
if (!ieee80211_hw_check(&local->hw, TX_AMSDU))
return false;
@@ -3228,8 +3219,19 @@ static bool ieee80211_amsdu_aggregate(st
if (max_frags && nfrags > max_frags)
goto out;
- if (!ieee80211_amsdu_realloc_pad(local, skb, sizeof(rfc1042_header) + 2,
- &subframe_len))
+ /*
+ * 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
+ * is the length of the full A-MSDU, but that works since each time
+ * we add a new subframe we pad out the previous one to a multiple
+ * of 4 and thus it no longer matters in the next round.
+ */
+ hdrlen = fast_tx->hdr_len - sizeof(rfc1042_header);
+ if ((head->len - hdrlen) & 3)
+ pad = 4 - ((head->len - hdrlen) & 3);
+
+ if (!ieee80211_amsdu_realloc_pad(local, skb, sizeof(rfc1042_header) +
+ 2 + pad))
goto out;
ret = true;
@@ -3241,6 +3243,8 @@ static bool ieee80211_amsdu_aggregate(st
memcpy(data, &len, 2);
memcpy(data + 2, rfc1042_header, sizeof(rfc1042_header));
+ memset(skb_push(skb, pad), 0, pad);
+
head->len += skb->len;
head->data_len += skb->len;
*frag_tail = skb;
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