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Subject[PATCH 4.20 196/352] mac80211: Properly handle SKB with radiotap only
Date
4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 8020919a9b99d6c990dc6a50e8215e291fbbe5a6 ]

The monitor interface Rx handling of SKBs that contain only
radiotap information was buggy as it tried to access the
SKB assuming it contains a frame.

To fix this, check the RX_FLAG_NO_PSDU flag in the Rx status
(indicting that the SKB contains only radiotap information),
and do not perform data path specific processing when the flag
is set.

Signed-off-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/mac80211/rx.c | 26 +++++++++++++++++---------
1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 428f7ad5f9b5..77d996a60f12 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -753,6 +753,7 @@ ieee80211_rx_monitor(struct ieee80211_local *local, struct sk_buff *origskb,
struct ieee80211_sub_if_data *monitor_sdata =
rcu_dereference(local->monitor_sdata);
bool only_monitor = false;
+ unsigned int min_head_len;

if (status->flag & RX_FLAG_RADIOTAP_HE)
rtap_space += sizeof(struct ieee80211_radiotap_he);
@@ -766,6 +767,8 @@ ieee80211_rx_monitor(struct ieee80211_local *local, struct sk_buff *origskb,
rtap_space += sizeof(*rtap) + rtap->len + rtap->pad;
}

+ min_head_len = rtap_space;
+
/*
* First, we may need to make a copy of the skb because
* (1) we need to modify it for radiotap (if not present), and
@@ -775,18 +778,23 @@ ieee80211_rx_monitor(struct ieee80211_local *local, struct sk_buff *origskb,
* the SKB because it has a bad FCS/PLCP checksum.
*/

- if (ieee80211_hw_check(&local->hw, RX_INCLUDES_FCS)) {
- if (unlikely(origskb->len <= FCS_LEN)) {
- /* driver bug */
- WARN_ON(1);
- dev_kfree_skb(origskb);
- return NULL;
+ if (!(status->flag & RX_FLAG_NO_PSDU)) {
+ if (ieee80211_hw_check(&local->hw, RX_INCLUDES_FCS)) {
+ if (unlikely(origskb->len <= FCS_LEN + rtap_space)) {
+ /* driver bug */
+ WARN_ON(1);
+ dev_kfree_skb(origskb);
+ return NULL;
+ }
+ present_fcs_len = FCS_LEN;
}
- present_fcs_len = FCS_LEN;
+
+ /* also consider the hdr->frame_control */
+ min_head_len += 2;
}

- /* ensure hdr->frame_control and vendor radiotap data are in skb head */
- if (!pskb_may_pull(origskb, 2 + rtap_space)) {
+ /* ensure that the expected data elements are in skb head */
+ if (!pskb_may_pull(origskb, min_head_len)) {
dev_kfree_skb(origskb);
return NULL;
}
--
2.19.1


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