linux-kernel - Re: [PATCH] clk: Mark fwnodes when their clock provider is added

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Date:   Thu, 25 Mar 2021 14:31:57 +0100
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Tudor Ambarus <tudor.ambarus@...rochip.com>, corbet@....net,
        gregkh@...uxfoundation.org, rafael@...nel.org, khilman@...nel.org,
        ulf.hansson@...aro.org, len.brown@...el.com, lenb@...nel.org,
        pavel@....cz, mturquette@...libre.com, sboyd@...nel.org,
        robh+dt@...nel.org, frowand.list@...il.com, maz@...nel.org,
        tglx@...utronix.de, saravanak@...gle.com
Cc:     nicolas.ferre@...rochip.com, claudiu.beznea@...rochip.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-acpi@...r.kernel.org,
        geert@...ux-m68k.org, kernel-team@...roid.com,
        linux-rpi-kernel <linux-rpi-kernel@...ts.infradead.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Subject: Re: [PATCH] clk: Mark fwnodes when their clock provider is added

Hi

On 10.02.2021 12:44, Tudor Ambarus wrote:
> This is a follow-up for:
> commit 3c9ea42802a1 ("clk: Mark fwnodes when their clock provider is added/removed")
>
> The above commit updated the deprecated of_clk_add_provider(),
> but missed to update the preferred of_clk_add_hw_provider().
> Update it now.
>
> Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>

This patch, which landed in linux-next as commit 6579c8d97ad7 ("clk: 
Mark fwnodes when their clock provider is added") causes the following 
NULL pointer dereference on Raspberry Pi 3b+ boards:

--->8---

raspberrypi-firmware soc:firmware: Attached to firmware from 
2020-01-06T13:05:25
Unable to handle kernel NULL pointer dereference at virtual address 
0000000000000050
Mem abort info:
   ESR = 0x96000004
   EC = 0x25: DABT (current EL), IL = 32 bits
   SET = 0, FnV = 0
   EA = 0, S1PTW = 0
Data abort info:
   ISV = 0, ISS = 0x00000004
   CM = 0, WnR = 0
[0000000000000050] user address but active_mm is swapper
Internal error: Oops: 96000004 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 10 Comm: kworker/0:1 Not tainted 5.12.0-rc4+ #2764
Hardware name: Raspberry Pi 3 Model B (DT)
Workqueue: events deferred_probe_work_func
pstate: 00000005 (nzcv daif -PAN -UAO -TCO BTYPE=--)
pc : of_clk_add_hw_provider+0xac/0xe8
lr : of_clk_add_hw_provider+0x94/0xe8
sp : ffff8000130936b0
x29: ffff8000130936b0 x28: ffff800012494e04
x27: ffff00003b18cb05 x26: ffff00003aa5c010
x25: 0000000000000000 x24: 0000000000000000
x23: ffff00003aa1e380 x22: ffff8000106830d0
x21: ffff80001233f180 x20: 0000000000000018
x19: 0000000000000000 x18: ffff8000124d38b0
x17: 0000000000000013 x16: 0000000000000014
x15: ffff8000125758b0 x14: 00000000000184e0
x13: 000000000000292e x12: ffff80001258dd98
x11: 0000000000000001 x10: 0101010101010101
x9 : ffff80001233f288 x8 : 7f7f7f7f7f7f7f7f
x7 : fefefefeff6c626f x6 : 5d636d8080808080
x5 : 00000000006d635d x4 : 0000000000000000
x3 : 0000000000000000 x2 : 540eb5edae191600
x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
  of_clk_add_hw_provider+0xac/0xe8
  devm_of_clk_add_hw_provider+0x5c/0xb8
  raspberrypi_clk_probe+0x110/0x210
  platform_probe+0x90/0xd8
  really_probe+0x108/0x3c0
  driver_probe_device+0x60/0xc0
  __device_attach_driver+0x9c/0xd0
  bus_for_each_drv+0x70/0xc8
  __device_attach+0xec/0x150
  device_initial_probe+0x10/0x18
  bus_probe_device+0x94/0xa0
  device_add+0x47c/0x780
  platform_device_add+0x110/0x248
  platform_device_register_full+0x120/0x150
  rpi_firmware_probe+0x158/0x1f8
  platform_probe+0x90/0xd8
  really_probe+0x108/0x3c0
  driver_probe_device+0x60/0xc0
  __device_attach_driver+0x9c/0xd0
  bus_for_each_drv+0x70/0xc8
  __device_attach+0xec/0x150
  device_initial_probe+0x10/0x18
  bus_probe_device+0x94/0xa0
  deferred_probe_work_func+0x70/0xa8
  process_one_work+0x2a8/0x718
  worker_thread+0x48/0x460
  kthread+0x134/0x160
  ret_from_fork+0x10/0x18
Code: b1006294 540000c0 b140069f 54000088 (3940e280)
---[ end trace 7ead5ec2f0c51cfe ]---

This patch mainly revealed that clk/bcm/clk-raspberrypi.c driver calls 
devm_of_clk_add_hw_provider(), with a device pointer, which has a NULL 
dev->of_node. I'm not sure if adding a check for a NULL np in 
of_clk_add_hw_provider() is a right fix, though.

> ---
>   drivers/clk/clk.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 27ff90eacb1f..9370e4dfecae 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -4594,6 +4594,8 @@ int of_clk_add_hw_provider(struct device_node *np,
>   	if (ret < 0)
>   		of_clk_del_provider(np);
>   
> +	fwnode_dev_initialized(&np->fwnode, true);
> +
>   	return ret;
>   }
>   EXPORT_SYMBOL_GPL(of_clk_add_hw_provider);

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland