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From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Thu, 14 Jul 2022 16:39:45 +0200
Message-ID: <CAPDyKFoRRxe8wUtJWfuDCxuz8wktUOyMD7jQApYGJO0zbax1Jw@mail.gmail.com>
Subject: Re: [PATCH v5] brcmfmac: prevent double-free on hardware-reset
To:     Arend Van Spriel <aspriel@gmail.com>
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>
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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.

Kind regards
Uffe