[PATCH] ath9k: Fix out-of-bound memcpy in ath9k_hif_usb_rx_stream

[Zekun Shen <bruceshenzk@gmail.com>]

Large pkt_len can lead to out-out-bound memcpy. Current
ath9k_hif_usb_rx_stream allows combining the content of two urb
inputs to one pkt. The first input can indicate the size of the
pkt. Any remaining size is saved in hif_dev->rx_remain_len.
While processing the next input, memcpy is used with rx_remain_len.

4-byte pkt_len can go up to 0xffff, while a single input is 0x4000
maximum in size (MAX_RX_BUF_SIZE). Thus, the patch adds a check for
pkt_len which must not exceed 2 * MAX_RX_BUG_SIZE.

BUG: KASAN: slab-out-of-bounds in ath9k_hif_usb_rx_cb+0x490/0xed7 [ath9k_htc]
Read of size 46393 at addr ffff888018798000 by task kworker/0:1/23

CPU: 0 PID: 23 Comm: kworker/0:1 Not tainted 5.6.0 #63
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.10.2-0-g5f4c7b1-prebuilt.qemu-project.org 04/01/2014
Workqueue: events request_firmware_work_func
Call Trace:
 <IRQ>
 dump_stack+0x76/0xa0
 print_address_description.constprop.0+0x16/0x200
 ? ath9k_hif_usb_rx_cb+0x490/0xed7 [ath9k_htc]
 ? ath9k_hif_usb_rx_cb+0x490/0xed7 [ath9k_htc]
 __kasan_report.cold+0x37/0x7c
 ? ath9k_hif_usb_rx_cb+0x490/0xed7 [ath9k_htc]
 kasan_report+0xe/0x20
 check_memory_region+0x15a/0x1d0
 memcpy+0x20/0x50
 ath9k_hif_usb_rx_cb+0x490/0xed7 [ath9k_htc]
 ? hif_usb_mgmt_cb+0x2d9/0x2d9 [ath9k_htc]
 ? _raw_spin_lock_irqsave+0x7b/0xd0
 ? _raw_spin_trylock_bh+0x120/0x120
 ? __usb_unanchor_urb+0x12f/0x210
 __usb_hcd_giveback_urb+0x1e4/0x380
 usb_giveback_urb_bh+0x241/0x4f0
 ? __hrtimer_run_queues+0x316/0x740
 ? __usb_hcd_giveback_urb+0x380/0x380
 tasklet_action_common.isra.0+0x135/0x330
 __do_softirq+0x18c/0x634
 irq_exit+0x114/0x140
 smp_apic_timer_interrupt+0xde/0x380
 apic_timer_interrupt+0xf/0x20

Signed-off-by: Zekun Shen <bruceshenzk@gmail.com>
---
 drivers/net/wireless/ath/ath9k/hif_usb.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/wireless/ath/ath9k/hif_usb.c b/drivers/net/wireless/ath/ath9k/hif_usb.c
index 860da13bf..0681bc5fa 100644
--- a/drivers/net/wireless/ath/ath9k/hif_usb.c
+++ b/drivers/net/wireless/ath/ath9k/hif_usb.c
@@ -589,6 +589,12 @@ static void ath9k_hif_usb_rx_stream(struct hif_device_usb *hif_dev,
 			RX_STAT_INC(skb_dropped);
 			return;
 		}
+		if (pkt_len > 2 * MAX_RX_BUF_SIZE) {
+			dev_err(&hif_dev->udev->dev,
+				"ath9k_htc: invalid pkt_len (%x)\n", pkt_len);
+			RX_STAT_INC(skb_dropped);
+			return;
+		}
 
 		pad_len = 4 - (pkt_len & 0x3);
 		if (pad_len == 4)
-- 
2.25.1