Subject: Re: [PATCH] rsi_usb: Fix use-after-free in rsi_rx_done_handler

From: Kalle Valo <[email-masked]>
Date: Mon, 01 Nov 2021 16:06:52 +0200

Zekun Shen <[email-masked]> writes:

> 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: Zekun Shen <[email-masked]>
> Reported-by: Brendan Dolan-Gavitt <[email-masked]>
> Signed-off-by: Zekun Shen <[email-masked]>

There's no need to have the author in Reported-by tag, so I'll remove
that.

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