[PATCH] net: stmmac: add explicit check and error on invalid PTP clock rate

[PATCH] net: stmmac: add explicit check and error on invalid PTP clock rate

[Alexis Lothoré]

While some platforms implementing dwmac open-code the clk_ptp_rate
value, some others dynamically retrieve the value at runtime. If the
retrieved value happens to be 0 for any reason, it will eventually
propagate up to PTP initialization when bringing up the interface,
leading to a divide by 0:

 Division by zero in kernel.
 CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.12.30-00001-g48313bd5768a #22
 Hardware name: STM32 (Device Tree Support)
 Call trace:
  unwind_backtrace from show_stack+0x18/0x1c
  show_stack from dump_stack_lvl+0x6c/0x8c
  dump_stack_lvl from Ldiv0_64+0x8/0x18
  Ldiv0_64 from stmmac_init_tstamp_counter+0x190/0x1a4
  stmmac_init_tstamp_counter from stmmac_hw_setup+0xc1c/0x111c
  stmmac_hw_setup from __stmmac_open+0x18c/0x434
  __stmmac_open from stmmac_open+0x3c/0xbc
  stmmac_open from __dev_open+0xf4/0x1ac
  __dev_open from __dev_change_flags+0x1cc/0x224
  __dev_change_flags from dev_change_flags+0x24/0x60
  dev_change_flags from ip_auto_config+0x2e8/0x11a0
  ip_auto_config from do_one_initcall+0x84/0x33c
  do_one_initcall from kernel_init_freeable+0x1b8/0x214
  kernel_init_freeable from kernel_init+0x24/0x140
  kernel_init from ret_from_fork+0x14/0x28
 Exception stack(0xe0815fb0 to 0xe0815ff8)

Prevent this division by 0 by adding an explicit check and error log
about the actual issue.

Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 918d7f2e8ba992208d7d6521a1e9dba01086058f..f68e3ece919cc88d0bf199a394bc7e44b5dee095 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -835,6 +835,11 @@ int stmmac_init_tstamp_counter(struct stmmac_priv *priv, u32 systime_flags)
 	if (!(priv->dma_cap.time_stamp || priv->dma_cap.atime_stamp))
 		return -EOPNOTSUPP;
 
+	if (!priv->plat->clk_ptp_rate) {
+		netdev_err(priv->dev, "Invalid PTP clock rate");
+		return -EINVAL;
+	}
+
 	stmmac_config_hw_tstamping(priv, priv->ptpaddr, systime_flags);
 	priv->systime_flags = systime_flags;
 

---
base-commit: e0e2f78243385e7188a57fcfceb6a19f723f1dff
change-id: 20250522-stmmac_tstamp_div-f55112f06029

Best regards,
-- 
Alexis Lothoré, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH] net: stmmac: add explicit check and error on invalid PTP clock rate

[Yanteng Si]

在 5/23/25 7:46 PM, Alexis Lothoré 写道:
> While some platforms implementing dwmac open-code the clk_ptp_rate
> value, some others dynamically retrieve the value at runtime. If the
> retrieved value happens to be 0 for any reason, it will eventually
> propagate up to PTP initialization when bringing up the interface,
> leading to a divide by 0:
> 
>   Division by zero in kernel.
>   CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.12.30-00001-g48313bd5768a #22
>   Hardware name: STM32 (Device Tree Support)
>   Call trace:
>    unwind_backtrace from show_stack+0x18/0x1c
>    show_stack from dump_stack_lvl+0x6c/0x8c
>    dump_stack_lvl from Ldiv0_64+0x8/0x18
>    Ldiv0_64 from stmmac_init_tstamp_counter+0x190/0x1a4
>    stmmac_init_tstamp_counter from stmmac_hw_setup+0xc1c/0x111c
>    stmmac_hw_setup from __stmmac_open+0x18c/0x434
>    __stmmac_open from stmmac_open+0x3c/0xbc
>    stmmac_open from __dev_open+0xf4/0x1ac
>    __dev_open from __dev_change_flags+0x1cc/0x224
>    __dev_change_flags from dev_change_flags+0x24/0x60
>    dev_change_flags from ip_auto_config+0x2e8/0x11a0
>    ip_auto_config from do_one_initcall+0x84/0x33c
>    do_one_initcall from kernel_init_freeable+0x1b8/0x214
>    kernel_init_freeable from kernel_init+0x24/0x140
>    kernel_init from ret_from_fork+0x14/0x28
>   Exception stack(0xe0815fb0 to 0xe0815ff8)
> 
> Prevent this division by 0 by adding an explicit check and error log
> about the actual issue.

 From your description, I cannot determine the scope
of "some platforms". My point is: if there are only
a few platforms, can we find a way to handle this in
the directory of the corresponding platform?

And there need a Fixes tag.


Thanks,
Yanteng
> 
> Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>
> ---
>   drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 918d7f2e8ba992208d7d6521a1e9dba01086058f..f68e3ece919cc88d0bf199a394bc7e44b5dee095 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -835,6 +835,11 @@ int stmmac_init_tstamp_counter(struct stmmac_priv *priv, u32 systime_flags)
>   	if (!(priv->dma_cap.time_stamp || priv->dma_cap.atime_stamp))
>   		return -EOPNOTSUPP;
>   
> +	if (!priv->plat->clk_ptp_rate) {
> +		netdev_err(priv->dev, "Invalid PTP clock rate");
> +		return -EINVAL;
> +	}
> +
>   	stmmac_config_hw_tstamping(priv, priv->ptpaddr, systime_flags);
>   	priv->systime_flags = systime_flags;
>   
> 
> ---
> base-commit: e0e2f78243385e7188a57fcfceb6a19f723f1dff
> change-id: 20250522-stmmac_tstamp_div-f55112f06029
> 
> Best regards,

Re: [PATCH] net: stmmac: add explicit check and error on invalid PTP clock rate

[Alexis Lothoré]

On Mon May 26, 2025 at 4:22 AM CEST, Yanteng Si wrote:
> 在 5/23/25 7:46 PM, Alexis Lothoré 写道:
>> While some platforms implementing dwmac open-code the clk_ptp_rate
>> value, some others dynamically retrieve the value at runtime. If the
>> retrieved value happens to be 0 for any reason, it will eventually
>> propagate up to PTP initialization when bringing up the interface,
>> leading to a divide by 0:

[...]

>  From your description, I cannot determine the scope
> of "some platforms". My point is: if there are only
> a few platforms, can we find a way to handle this in
> the directory of the corresponding platform?

From what I can see, it can affect any platform using the stmmac driver as
the platform driver (except maybe dwmac-qcom-ethqos.c, which enforces an
open-coded clk_ptp_rate after the stmmac_probe_config_dt call that sets
the clk_ptp_rate), if the platform declares a dedicated clk_ptp_ref clock.
So I would rather say that it can affect most of the platforms.

In my case, I have observed the issue with the dwmac-stm32.c driver, on an
STM32MP157a-dk1 platform.

> And there need a Fixes tag.

Ok, I'll add a relevant Fixes tag.

Alexis

>> Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>
>> ---
>>   drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>> 
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> index 918d7f2e8ba992208d7d6521a1e9dba01086058f..f68e3ece919cc88d0bf199a394bc7e44b5dee095 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> @@ -835,6 +835,11 @@ int stmmac_init_tstamp_counter(struct stmmac_priv *priv, u32 systime_flags)
>>   	if (!(priv->dma_cap.time_stamp || priv->dma_cap.atime_stamp))
>>   		return -EOPNOTSUPP;
>>   
>> +	if (!priv->plat->clk_ptp_rate) {
>> +		netdev_err(priv->dev, "Invalid PTP clock rate");
>> +		return -EINVAL;
>> +	}
>> +
>>   	stmmac_config_hw_tstamping(priv, priv->ptpaddr, systime_flags);
>>   	priv->systime_flags = systime_flags;
>>   
>> 
>> ---
>> base-commit: e0e2f78243385e7188a57fcfceb6a19f723f1dff
>> change-id: 20250522-stmmac_tstamp_div-f55112f06029
>> 
>> Best regards,




-- 
Alexis Lothoré, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH] net: stmmac: add explicit check and error on invalid PTP clock rate

[Yanteng Si]

在 5/26/25 10:42 PM, Alexis Lothoré 写道:
> On Mon May 26, 2025 at 4:22 AM CEST, Yanteng Si wrote:
>> 在 5/23/25 7:46 PM, Alexis Lothoré 写道:
>>> While some platforms implementing dwmac open-code the clk_ptp_rate
>>> value, some others dynamically retrieve the value at runtime. If the
>>> retrieved value happens to be 0 for any reason, it will eventually
>>> propagate up to PTP initialization when bringing up the interface,
>>> leading to a divide by 0:
> [...]
>
>>   From your description, I cannot determine the scope
>> of "some platforms". My point is: if there are only
>> a few platforms, can we find a way to handle this in
>> the directory of the corresponding platform?
>  From what I can see, it can affect any platform using the stmmac driver as
> the platform driver (except maybe dwmac-qcom-ethqos.c, which enforces an
> open-coded clk_ptp_rate after the stmmac_probe_config_dt call that sets
> the clk_ptp_rate), if the platform declares a dedicated clk_ptp_ref clock.
> So I would rather say that it can affect most of the platforms.
>
> In my case, I have observed the issue with the dwmac-stm32.c driver, on an
> STM32MP157a-dk1 platform.
Okay!
>
>> And there need a Fixes tag.
> Ok, I'll add a relevant Fixes tag.

On this premise,


Reviewed-by: Yanteng Si <si.yanteng@linux.dev>


Thanks,

Yanteng

>
> Alexis
>
>>> Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>
>>> ---
>>>    drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 5 +++++
>>>    1 file changed, 5 insertions(+)
>>>
>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>>> index 918d7f2e8ba992208d7d6521a1e9dba01086058f..f68e3ece919cc88d0bf199a394bc7e44b5dee095 100644
>>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>>> @@ -835,6 +835,11 @@ int stmmac_init_tstamp_counter(struct stmmac_priv *priv, u32 systime_flags)
>>>    	if (!(priv->dma_cap.time_stamp || priv->dma_cap.atime_stamp))
>>>    		return -EOPNOTSUPP;
>>>    
>>> +	if (!priv->plat->clk_ptp_rate) {
>>> +		netdev_err(priv->dev, "Invalid PTP clock rate");
>>> +		return -EINVAL;
>>> +	}
>>> +
>>>    	stmmac_config_hw_tstamping(priv, priv->ptpaddr, systime_flags);
>>>    	priv->systime_flags = systime_flags;
>>>    
>>>
>>> ---
>>> base-commit: e0e2f78243385e7188a57fcfceb6a19f723f1dff
>>> change-id: 20250522-stmmac_tstamp_div-f55112f06029
>>>
>>> Best regards,
>
>
>