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ath10k: fix peer stats null pointer dereference 

There was a race condition in SMP that an ath10k_peer was created but its
member sta was null. Following are procedures of ath10k_peer creation and
member sta access in peer statistics path.

    1. Peer creation:
        ath10k_peer_create()
            =>ath10k_wmi_peer_create()
                =>ath10k_wait_for_peer_created()
                ...

        # another kernel path, RX from firmware
        ath10k_htt_t2h_msg_handler()
        =>ath10k_peer_map_event()
                =>wake_up()
                # ar->peer_map[id] = peer //add peer to map

        #wake up original path from waiting
                ...
                # peer->sta = sta //sta assignment

    2.  RX path of statistics
        ath10k_htt_t2h_msg_handler()
            =>ath10k_update_per_peer_tx_stats()
                =>ath10k_htt_fetch_peer_stats()
                # peer->sta //sta accessing

Any access of peer->sta after peer was added to peer_map but before sta was
assigned could cause a null pointer issue. And because these two steps are
asynchronous, no proper lock can protect them. So both peer and sta need to
be checked before access.

Tested: QCA9984 with firmware ver 10.4-3.9.0.1-00005
Signed-off-by: Zhi Chen <zhichen@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
This commit is contained in:
Zhi Chen 2018-12-20 14:24:43 +02:00 committed by Kalle Valo
parent a3542d0c73
commit 2d3b55853b
2 changed files with 3 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/net/wireless/ath/ath10k/debugfs_sta.c
View File

@ -71,7 +71,7 @@ void ath10k_sta_update_rx_tid_stats_ampdu(struct ath10k *ar, u16 peer_id, u8 tid
spin_lock_bh(&ar->data_lock);
peer = ath10k_peer_find_by_id(ar, peer_id);
if (!peer)
if (!peer || !peer->sta)
goto out;
arsta = (struct ath10k_sta *)peer->sta->drv_priv;

4
drivers/net/wireless/ath/ath10k/htt_rx.c
View File

@ -3121,7 +3121,7 @@ static void ath10k_htt_fetch_peer_stats(struct ath10k *ar,
rcu_read_lock();
spin_lock_bh(&ar->data_lock);
peer = ath10k_peer_find_by_id(ar, peer_id);
if (!peer) {
if (!peer || !peer->sta) {
ath10k_warn(ar, "Invalid peer id %d peer stats buffer\n",
peer_id);
goto out;
@ -3174,7 +3174,7 @@ static void ath10k_fetch_10_2_tx_stats(struct ath10k *ar, u8 *data)
rcu_read_lock();
spin_lock_bh(&ar->data_lock);
peer = ath10k_peer_find_by_id(ar, peer_id);
if (!peer) {
if (!peer || !peer->sta) {
ath10k_warn(ar, "Invalid peer id %d in peer stats buffer\n",
peer_id);
goto out;