linux-kernel - Re: [PATCH] driver core: bus: Handle early calls to bus_to

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Date:   Tue, 28 Feb 2023 11:57:02 +0100
From:   Wolfram Sang <wsa@...nel.org>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Lee Jones <lee@...nel.org>,
        linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH] driver core: bus: Handle early calls to bus_to_subsys()

On Tue, Feb 21, 2023 at 01:53:51PM +0100, Geert Uytterhoeven wrote:
> When calling soc_device_match() from early_initcall(), bus_kset is still
> NULL, causing a crash:
> 
>     Unable to handle kernel NULL pointer dereference at virtual address 0000000000000028
>     ...
>     Call trace:
>      __lock_acquire+0x530/0x20f0
>      lock_acquire.part.0+0xc8/0x210
>      lock_acquire+0x64/0x80
>      _raw_spin_lock+0x4c/0x60
>      bus_to_subsys+0x24/0xac
>      bus_for_each_dev+0x30/0xcc
>      soc_device_match+0x4c/0xe0
>      r8a7795_sysc_init+0x18/0x60
>      rcar_sysc_pd_init+0xb0/0x33c
>      do_one_initcall+0x128/0x2bc
> 
> Before, bus_for_each_dev() handled this gracefully by checking that
> the back-pointer to the private structure was valid.
> 
> Fix this by adding a NULL check for bus_kset to bus_to_subsys().
> 
> Fixes: 83b9148df2c95e23 ("driver core: bus: bus iterator cleanups")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>

Current top-of-head doesn't boot my Salvator-XS board, this patch fixed
it.

Tested-by: Wolfram Sang <wsa+renesas@...g-engineering.com>


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