Minsuk Kang <linuxlovemin@xxxxxxxxxxxx> writes:
> Fix a stack-out-of-bounds write that occurs in a WMI response callback
> function that is called after a timeout occurs in ath9k_wmi_cmd().
> The callback writes to wmi->cmd_rsp_buf, a stack-allocated buffer that
> could no longer be valid when a timeout occurs. Checking seq_no is
> insufficient as the bug can occur between the timeout and the next WMI
> command. Add wmi->timedout to check whether a timeout occurred.
>
> Found by a modified version of syzkaller.
>
> BUG: KASAN: stack-out-of-bounds in ath9k_wmi_ctrl_rx
> Write of size 4
> Call Trace:
> memcpy
> ath9k_wmi_ctrl_rx
> ath9k_htc_rx_msg
> ath9k_hif_usb_reg_in_cb
> __usb_hcd_giveback_urb
> usb_hcd_giveback_urb
> dummy_timer
> call_timer_fn
> run_timer_softirq
> __do_softirq
> irq_exit_rcu
> sysvec_apic_timer_interrupt
>
> Signed-off-by: Minsuk Kang <linuxlovemin@xxxxxxxxxxxx>
> ---
> drivers/net/wireless/ath/ath9k/wmi.c | 5 ++++-
> drivers/net/wireless/ath/ath9k/wmi.h | 1 +
> 2 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/ath/ath9k/wmi.c b/drivers/net/wireless/ath/ath9k/wmi.c
> index f315c54bd3ac..f46cbecc12e3 100644
> --- a/drivers/net/wireless/ath/ath9k/wmi.c
> +++ b/drivers/net/wireless/ath/ath9k/wmi.c
> @@ -234,7 +234,8 @@ static void ath9k_wmi_ctrl_rx(void *priv, struct sk_buff *skb,
>
> /* Check if there has been a timeout. */
> spin_lock_irqsave(&wmi->wmi_lock, flags);
> - if (be16_to_cpu(hdr->seq_no) != wmi->last_seq_id) {
> + if (be16_to_cpu(hdr->seq_no) != wmi->last_seq_id ||
> + wmi->timedout) {
> spin_unlock_irqrestore(&wmi->wmi_lock, flags);
> goto free_skb;
> }
> @@ -290,6 +291,7 @@ static int ath9k_wmi_cmd_issue(struct wmi *wmi,
>
> spin_lock_irqsave(&wmi->wmi_lock, flags);
> wmi->last_seq_id = wmi->tx_seq_id;
> + wmi->timedout = false;
> spin_unlock_irqrestore(&wmi->wmi_lock, flags);
>
> return htc_send_epid(wmi->htc, skb, wmi->ctrl_epid);
> @@ -341,6 +343,7 @@ int ath9k_wmi_cmd(struct wmi *wmi, enum wmi_cmd_id cmd_id,
> if (!time_left) {
> ath_dbg(common, WMI, "Timeout waiting for WMI command: %s\n",
> wmi_cmd_to_name(cmd_id));
> + wmi->timedout = true;
Instead of introducing a new 'timedout' field, why not just reset
last_seq_id to 0 here? That way the existing check should trigger the
abort in ath9k_wmi_ctrl_rx()...
-Toke
