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Subject[PATCH 5.4 198/320] ath9k: Fix out-of-bound memcpy in ath9k_hif_usb_rx_stream
Date
From: Zekun Shen <bruceshenzk@gmail.com>

[ Upstream commit 6ce708f54cc8d73beca213cec66ede5ce100a781 ]

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

I found the bug using a custome USBFuzz port. It's a research work
to fuzz USB stack/drivers. I modified it to fuzz ath9k driver only,
providing hand-crafted usb descriptors to QEMU.

After fixing the value of pkt_tag to ATH_USB_RX_STREAM_MODE_TAG in QEMU
emulation, I found the KASAN report. The bug is triggerable whenever
pkt_len is above two MAX_RX_BUG_SIZE. I used the same input that crashes
to test the driver works when applying the patch.

Signed-off-by: Zekun Shen <bruceshenzk@gmail.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/YXsidrRuK6zBJicZ@10-18-43-117.dynapool.wireless.nyu.edu
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/wireless/ath/ath9k/hif_usb.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/net/wireless/ath/ath9k/hif_usb.c b/drivers/net/wireless/ath/ath9k/hif_usb.c
index 2ed98aaed6fb5..c8c7afe0e343e 100644
--- a/drivers/net/wireless/ath/ath9k/hif_usb.c
+++ b/drivers/net/wireless/ath/ath9k/hif_usb.c
@@ -590,6 +590,13 @@ static void ath9k_hif_usb_rx_stream(struct hif_device_usb *hif_dev,
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)
pad_len = 0;
--
2.34.1


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