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>

diff --git a/drivers/net/wireless/ath/ath10k/debugfs_sta.c b/drivers/net/wireless/ath/ath10k/debugfs_sta.c
index 0f3fd65a459e2454c32cda1875c2515f77476711..4778a455d81a97d927a52b6b4df9b52ac3c96f63 100644 (file)
--- a/drivers/net/wireless/ath/ath10k/debugfs_sta.c
+++ b/drivers/net/wireless/ath/ath10k/debugfs_sta.c
@@ -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;

diff --git a/drivers/net/wireless/ath/ath10k/htt_rx.c b/drivers/net/wireless/ath/ath10k/htt_rx.c
index 7bc1c9545e47d9f3630009ddb682d59a47bbe7e9..f42bac204ef81a4089be1f2691e1dece731e14eb 100644 (file)
--- a/drivers/net/wireless/ath/ath10k/htt_rx.c
+++ b/drivers/net/wireless/ath/ath10k/htt_rx.c
@@ -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;