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Message-ID: <cbdd5e41-7538-6d8f-344a-54a816c6d511@canonical.com>
Date:   Wed, 9 Mar 2022 10:52:11 +0100
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Subject: Re: [PATCH] NFC: port100: fix use-after-free in port100_send_complete
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To:     Pavel Skripkin <paskripkin@gmail.com>, sameo@linux.intel.com,
        thierry.escande@linux.intel.com
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        syzbot+16bcb127fb73baeecb14@syzkaller.appspotmail.com
References: <20220308185007.6987-1-paskripkin@gmail.com>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
In-Reply-To: <20220308185007.6987-1-paskripkin@gmail.com>
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On 08/03/2022 19:50, Pavel Skripkin wrote:
> Syzbot reported UAF in port100_send_complete(). The root case is in
> missing usb_kill_urb() calls on error handling path of ->probe function.
> 
> port100_send_complete() accesses devm allocated memory which will be
> freed on probe failure. We should kill this urbs before returning an
> error from probe function to prevent reported use-after-free
> 
> Fail log:
> 
> BUG: KASAN: use-after-free in port100_send_complete+0x16e/0x1a0 drivers/nfc/port100.c:935
> Read of size 1 at addr ffff88801bb59540 by task ksoftirqd/2/26
> ...
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
>  print_address_description.constprop.0.cold+0x8d/0x303 mm/kasan/report.c:255
>  __kasan_report mm/kasan/report.c:442 [inline]
>  kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
>  port100_send_complete+0x16e/0x1a0 drivers/nfc/port100.c:935
>  __usb_hcd_giveback_urb+0x2b0/0x5c0 drivers/usb/core/hcd.c:1670
> 
> ...
> 
> Allocated by task 1255:
>  kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
>  kasan_set_track mm/kasan/common.c:45 [inline]
>  set_alloc_info mm/kasan/common.c:436 [inline]
>  ____kasan_kmalloc mm/kasan/common.c:515 [inline]
>  ____kasan_kmalloc mm/kasan/common.c:474 [inline]
>  __kasan_kmalloc+0xa6/0xd0 mm/kasan/common.c:524
>  alloc_dr drivers/base/devres.c:116 [inline]
>  devm_kmalloc+0x96/0x1d0 drivers/base/devres.c:823
>  devm_kzalloc include/linux/device.h:209 [inline]
>  port100_probe+0x8a/0x1320 drivers/nfc/port100.c:1502
> 
> Freed by task 1255:
>  kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
>  kasan_set_track+0x21/0x30 mm/kasan/common.c:45
>  kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
>  ____kasan_slab_free mm/kasan/common.c:366 [inline]
>  ____kasan_slab_free+0xff/0x140 mm/kasan/common.c:328
>  kasan_slab_free include/linux/kasan.h:236 [inline]
>  __cache_free mm/slab.c:3437 [inline]
>  kfree+0xf8/0x2b0 mm/slab.c:3794
>  release_nodes+0x112/0x1a0 drivers/base/devres.c:501
>  devres_release_all+0x114/0x190 drivers/base/devres.c:530
>  really_probe+0x626/0xcc0 drivers/base/dd.c:670
> 
> Reported-and-tested-by: syzbot+16bcb127fb73baeecb14@syzkaller.appspotmail.com
> Fixes: 0347a6ab300a ("NFC: port100: Commands mechanism implementation")
> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
> ---
>  drivers/nfc/port100.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/nfc/port100.c b/drivers/nfc/port100.c
> index d7db1a0e6be1..00d8ea6dcb5d 100644
> --- a/drivers/nfc/port100.c
> +++ b/drivers/nfc/port100.c
> @@ -1612,7 +1612,9 @@ static int port100_probe(struct usb_interface *interface,
>  	nfc_digital_free_device(dev->nfc_digital_dev);
>  
>  error:
> +	usb_kill_urb(dev->in_urb);
>  	usb_free_urb(dev->in_urb);
> +	usb_kill_urb(dev->out_urb);
>  	usb_free_urb(dev->out_urb);
>  	usb_put_dev(dev->udev);


Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>

Thanks, this looks good. I think I saw similar patterns also in other
drivers, e.g. pn533. I will check it later, but if you have spare time,
feel free to investigate.

Similar cases (unresolved):
https://syzkaller.appspot.com/bug?extid=1dc8b460d6d48d7ef9ca
https://syzkaller.appspot.com/bug?extid=abd2e0dafb481b621869
https://syzkaller.appspot.com/bug?extid=dbec6695a6565a9c6bc0


Best regards,
Krzysztof