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Date:   Fri, 15 Jul 2022 15:19:15 +0200
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Subject: Re: [PATCH v5] brcmfmac: prevent double-free on hardware-reset
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To:     Ulf Hansson <ulf.hansson@linaro.org>
Cc:     Danny van Heumen <danny@dannyvanheumen.nl>,
        "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
        Franky Lin <franky.lin@broadcom.com>,
        Hante Meuleman <hante.meuleman@broadcom.com>
References: <id1HN6qCMAirApBzTA6fT7ZFWBBGCJhULpflxQ7NT6cgCboVnn3RHpiOFjA9SbRqzBRFLk9ES0C4FNvO6fUQsNg7pqF6ZSNAYUo99nHy8PY=@dannyvanheumen.nl>
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 <CAPDyKFoRRxe8wUtJWfuDCxuz8wktUOyMD7jQApYGJO0zbax1Jw@mail.gmail.com>
From:   Arend Van Spriel <aspriel@gmail.com>
In-Reply-To: <CAPDyKFoRRxe8wUtJWfuDCxuz8wktUOyMD7jQApYGJO0zbax1Jw@mail.gmail.com>
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On 7/14/2022 4:39 PM, Ulf Hansson wrote:
> On Thu, 14 Jul 2022 at 14:49, Arend Van Spriel <aspriel@gmail.com> wrote:
>>
>> On 7/14/2022 12:04 PM, Ulf Hansson wrote:
>>> On Tue, 12 Jul 2022 at 01:22, Danny van Heumen <danny@dannyvanheumen.nl> wrote:
>>>>
>>>> In case of buggy firmware, brcmfmac may perform a hardware reset. If during
>>>> reset and subsequent probing an early failure occurs, a memory region is
>>>> accidentally double-freed. With hardened memory allocation enabled, this error
>>>> will be detected.
>>>>
>>>> - return early where appropriate to skip unnecessary clean-up.
>>>> - set '.freezer' pointer to NULL to prevent double-freeing under possible
>>>>     other circumstances and to re-align result under various different
>>>>     behaviors of memory allocation freeing.
>>>> - correctly claim host on func1 for disabling func2.
>>>> - after reset, do not initiate probing immediately, but rely on events.
>>>>
>>>> Given a firmware crash, function 'brcmf_sdio_bus_reset' is called. It calls
>>>> 'brcmf_sdiod_remove', then follows up with 'brcmf_sdiod_probe' to reinitialize
>>>> the hardware. If 'brcmf_sdiod_probe' fails to "set F1 blocksize", it exits
>>>> early, which includes calling 'brcmf_sdiod_remove'. In both cases
>>>> 'brcmf_sdiod_freezer_detach' is called to free allocated '.freezer', which
>>>> has not yet been re-allocated the second time.
>>>>
>>>> Stacktrace of (failing) hardware reset after firmware-crash:
>>>>
>>>> Code: b9402b82 8b0202c0 eb1a02df 54000041 (d4210000)
>>>>    ret_from_fork+0x10/0x20
>>>>    kthread+0x154/0x160
>>>>    worker_thread+0x188/0x504
>>>>    process_one_work+0x1f4/0x490
>>>>    brcmf_core_bus_reset+0x34/0x44 [brcmfmac]
>>>>    brcmf_sdio_bus_reset+0x68/0xc0 [brcmfmac]
>>>>    brcmf_sdiod_probe+0x170/0x21c [brcmfmac]
>>>>    brcmf_sdiod_remove+0x48/0xc0 [brcmfmac]
>>>>    kfree+0x210/0x220
>>>>    __slab_free+0x58/0x40c
>>>> Call trace:
>>>> x2 : 0000000000000040 x1 : fffffc00002d2b80 x0 : ffff00000b4aee40
>>>> x5 : ffff8000013fa728 x4 : 0000000000000001 x3 : ffff00000b4aee00
>>>> x8 : ffff800009967ce0 x7 : ffff8000099bfce0 x6 : 00000006f8005d01
>>>> x11: ffff8000099bfce0 x10: 00000000fffff000 x9 : ffff8000083401d0
>>>> x14: 0000000000000000 x13: 657a69736b636f6c x12: 6220314620746573
>>>> x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000030
>>>> x20: fffffc00002d2ba0 x19: fffffc00002d2b80 x18: 0000000000000000
>>>> x23: ffff00000b4aee00 x22: ffff00000b4aee00 x21: 0000000000000001
>>>> x26: ffff00000b4aee00 x25: ffff0000f7753705 x24: 000000000001288a
>>>> x29: ffff80000a22bbf0 x28: ffff000000401200 x27: 000000008020001a
>>>> sp : ffff80000a22bbf0
>>>> lr : kfree+0x210/0x220
>>>> pc : __slab_free+0x58/0x40c
>>>> pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>>>> Workqueue: events brcmf_core_bus_reset [brcmfmac]
>>>> Hardware name: Pine64 Pinebook Pro (DT)
>>>> CPU: 2 PID: 639 Comm: kworker/2:2 Tainted: G         C        5.16.0-0.bpo.4-arm64 #1  Debian 5.16.12-1~bpo11+1
>>>>    nvmem_rockchip_efuse industrialio_triggered_buffer videodev snd_soc_core snd_pcm_dmaengine kfifo_buf snd_pcm io_domain mc industrialio mt>
>>>> Modules linked in: snd_seq_dummy snd_hrtimer snd_seq snd_seq_device nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reje>
>>>> Internal error: Oops - BUG: 0 [#1] SMP
>>>> kernel BUG at mm/slub.c:379!
>>>>
>>>> Signed-off-by: Danny van Heumen <danny@dannyvanheumen.nl>
>>>
>>> I have to admit that, to me, it looks a bit weird to have one driver
>>> instance managing two different SDIO func devices. On the other hand,
>>> I don't know the HW so there might be good reasons for why.
>>>
>>> In any case, I want to point out a commit [1] for the mwifiex driver,
>>> which could serve as a good inspiration of how to make use of the
>>> mmc_hw_reset(). For example, one may look at the return code from
>>> mmc_hw_reset() to understand whether the reset will be done
>>> synchronous or asynchronous (via device re-registration).
>>
>> Thanks, Uffe
>>
>> Could the API be extended so the caller can request the reset to be
>> asynchronous.
> 
> Yes, that should be fine. The current behaviour is that it will be
> asynchronous if there are more than one SDIO func device bound to a
> driver.

I see. So for brcmfmac we fall into that category. Thanks for the info.

Regards,
Arend