[PATCH 5.4 171/320] rsi: Fix use-after-free in rsi_rx_done_handler()

Greg Kroah-Hartman
2022-01-24T20:13:45Z

From: Zekun Shen <bruceshenzk@gmail.com>

[ Upstream commit b07e3c6ebc0c20c772c0f54042e430acec2945c3 ]

When freeing rx_cb->rx_skb, the pointer is not set to NULL,
a later rsi_rx_done_handler call will try to read the freed
address.
This bug will very likley lead to double free, although
detected early as use-after-free bug.

The bug is triggerable with a compromised/malfunctional usb
device. After applying the patch, the same input no longer
triggers the use-after-free.

Attached is the kasan report from fuzzing.

BUG: KASAN: use-after-free in rsi_rx_done_handler+0x354/0x430 [rsi_usb]
Read of size 4 at addr ffff8880188e5930 by task modprobe/231
Call Trace:
<IRQ>
dump_stack+0x76/0xa0
print_address_description.constprop.0+0x16/0x200
? rsi_rx_done_handler+0x354/0x430 [rsi_usb]
? rsi_rx_done_handler+0x354/0x430 [rsi_usb]
__kasan_report.cold+0x37/0x7c
? dma_direct_unmap_page+0x90/0x110
? rsi_rx_done_handler+0x354/0x430 [rsi_usb]
kasan_report+0xe/0x20
rsi_rx_done_handler+0x354/0x430 [rsi_usb]
__usb_hcd_giveback_urb+0x1e4/0x380
usb_giveback_urb_bh+0x241/0x4f0
? __usb_hcd_giveback_urb+0x380/0x380
? apic_timer_interrupt+0xa/0x20
tasklet_action_common.isra.0+0x135/0x330
__do_softirq+0x18c/0x634
? handle_irq_event+0xcd/0x157
? handle_edge_irq+0x1eb/0x7b0
irq_exit+0x114/0x140
do_IRQ+0x91/0x1e0
common_interrupt+0xf/0xf
</IRQ>

Reported-by: Brendan Dolan-Gavitt <brendandg@nyu.edu>
Signed-off-by: Zekun Shen <bruceshenzk@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/YXxQL/vIiYcZUu/j@10-18-43-117.dynapool.wireless.nyu.edu
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/wireless/rsi/rsi_91x_usb.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/rsi/rsi_91x_usb.c b/drivers/net/wireless/rsi/rsi_91x_usb.c
index 68ce3d2bc5357..730d7bf86c40c 100644
--- a/drivers/net/wireless/rsi/rsi_91x_usb.c
+++ b/drivers/net/wireless/rsi/rsi_91x_usb.c
@@ -261,8 +261,12 @@ static void rsi_rx_done_handler(struct urb *urb)
struct rsi_91x_usbdev *dev = (struct rsi_91x_usbdev *)rx_cb->data;
int status = -EINVAL;

+ if (!rx_cb->rx_skb)
+ return;
+
if (urb->status) {
dev_kfree_skb(rx_cb->rx_skb);
+ rx_cb->rx_skb = NULL;
return;
}

@@ -286,8 +290,10 @@ out:
if (rsi_rx_urb_submit(dev->priv, rx_cb->ep_num, GFP_ATOMIC))
rsi_dbg(ERR_ZONE, "%s: Failed in urb submission", __func__);

- if (status)
+ if (status) {
dev_kfree_skb(rx_cb->rx_skb);
+ rx_cb->rx_skb = NULL;
+ }
}

static void rsi_rx_urb_kill(struct rsi_hw *adapter, u8 ep_num)
--
2.34.1