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Date:   Mon, 25 Apr 2022 17:09:34 +0800 (GMT+08:00)
From:   duoming@....edu.cn
To:     "Krzysztof Kozlowski" <krzysztof.kozlowski@...aro.org>
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        broonie@...nel.org, akpm@...ux-foundation.org,
        alexander.deucher@....com, gregkh@...uxfoundation.org,
        davem@...emloft.net, linma@....edu.cn
Subject: Re: Re: [PATCH] drivers: nfc: nfcmrvl: reorder destructive
 operations in nfcmrvl_nci_unregister_dev to avoid bugs

Hello,

On Mon, 25 Apr 2022 09:59:32 +0200 Krzysztof wrote:

> > There are destructive operations such as nfcmrvl_fw_dnld_abort and
> > gpio_free in nfcmrvl_nci_unregister_dev. The resources such as firmware,
> > gpio and so on could be destructed while the upper layer functions such as
> > nfcmrvl_fw_dnld_start and nfcmrvl_nci_recv_frame is executing, which leads
> > to double-free, use-after-free and null-ptr-deref bugs.
> 
> You need to correct the subject prefix because it does not describe the
> subsystem (git log oneline --).

I will change the subject prefix to "nfc: nfcmrvl: uart: ".

> > 
> > There are three situations that could lead to double-free bugs.
> > 
> > The first situation is shown below:
> > 
> >    (Thread 1)                 |      (Thread 2)
> > nfcmrvl_fw_dnld_start         |
> >  ...                          |  nfcmrvl_nci_unregister_dev
> >  release_firmware()           |   nfcmrvl_fw_dnld_abort
> >   kfree(fw) //(1)             |    fw_dnld_over
> >                               |     release_firmware
> >   ...                         |      kfree(fw) //(2)
> >                               |     ...
> > 
> > The second situation is shown below:
> > 
> >    (Thread 1)                 |      (Thread 2)
> > nfcmrvl_fw_dnld_start         |
> >  ...                          |
> >  mod_timer                    |
> >  (wait a time)                |
> >  fw_dnld_timeout              |  nfcmrvl_nci_unregister_dev
> >    fw_dnld_over               |   nfcmrvl_fw_dnld_abort
> >     release_firmware          |    fw_dnld_over
> >      kfree(fw) //(1)          |     release_firmware
> >      ...                      |      kfree(fw) //(2)
> > 
> > The third situation is shown below:
> > 
> >        (Thread 1)               |       (Thread 2)
> > nfcmrvl_nci_recv_frame          |
> >  if(..->fw_download_in_progress)|
> >   nfcmrvl_fw_dnld_recv_frame    |
> >    queue_work                   |
> >                                 |
> > fw_dnld_rx_work                 | nfcmrvl_nci_unregister_dev
> >  fw_dnld_over                   |  nfcmrvl_fw_dnld_abort
> >   release_firmware              |   fw_dnld_over
> >    kfree(fw) //(1)              |    release_firmware
> >                                 |     kfree(fw) //(2)
> > 
> > The firmware struct is deallocated in position (1) and deallocated
> > in position (2) again.
> > 
> > The crash trace triggered by POC is like below:
> > 
> > [  122.640457] BUG: KASAN: double-free or invalid-free in fw_dnld_over+0x28/0xf0
> > [  122.640457] Call Trace:
> > [  122.640457]  <TASK>
> > [  122.640457]  kfree+0xb0/0x330
> > [  122.640457]  fw_dnld_over+0x28/0xf0
> > [  122.640457]  nfcmrvl_nci_unregister_dev+0x61/0x70
> > [  122.640457]  nci_uart_tty_close+0x87/0xd0
> > [  122.640457]  tty_ldisc_kill+0x3e/0x80
> > [  122.640457]  tty_ldisc_hangup+0x1b2/0x2c0
> > [  122.640457]  __tty_hangup.part.0+0x316/0x520
> > [  122.640457]  tty_release+0x200/0x670
> > [  122.640457]  __fput+0x110/0x410
> > [  122.640457]  task_work_run+0x86/0xd0
> > [  122.640457]  exit_to_user_mode_prepare+0x1aa/0x1b0
> > [  122.640457]  syscall_exit_to_user_mode+0x19/0x50
> > [  122.640457]  do_syscall_64+0x48/0x90
> > [  122.640457]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > [  122.640457] RIP: 0033:0x7f68433f6beb
> > 
> > What's more, there are also use-after-free and null-ptr-deref bugs
> > in nfcmrvl_fw_dnld_start. If we deallocate firmware struct, gpio or
> > set null to the members of priv->fw_dnld in nfcmrvl_nci_unregister_dev,
> > then, we dereference firmware, gpio or the members of priv->fw_dnld in
> > nfcmrvl_fw_dnld_start, the UAF or NPD bugs will happen.
> > 
> > This patch reorders destructive operations after nci_unregister_device
> > to avoid the double-free, UAF and NPD bugs, as nci_unregister_device
> > is well synchronized and won't return if there is a running routine.
> > This was mentioned in commit 3e3b5dfcd16a ("NFC: reorder the logic in
> > nfc_{un,}register_device").
> > 
> > Fixes: 3194c6870158 ("NFC: nfcmrvl: add firmware download support")
> > Signed-off-by: Duoming Zhou <duoming@....edu.cn>
> > Reviewed-by: Lin Ma <linma@....edu.cn>
> 
> It's the first submission, how this review appeared?

I will remove the review tag.

> On the other hand, you already sent something similar, so is it a v2? I
> am sorry but this is very confusing. Looks like
> https://lore.kernel.org/all/20220425005718.33639-1-duoming@zju.edu.cn/
> but there is no changelog and commit description is different.

I am sorry the above link is just a test, I forget to remove "Cc: stable@...r.kernel.org".

> Please read:
> https://elixir.bootlin.com/linux/v5.18-rc4/source/Documentation/process/submitting-patches.rst
> 

I will send "[PATCH net V2] nfc: nfcmrvl: uart: reorder destructive operations in nfcmrvl_nci_unregister_dev to avoid bugs".

Best regards,
Duoming Zhou

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