linux-kernel - Re: [PATCH] [v2] module: don't ignore sysfs_create

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Message-Id: <5fb74d31-a5f7-4fc0-96f0-f69158829df3@app.fastmail.com>
Date: Tue, 26 Mar 2024 15:12:46 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
 "Arnd Bergmann" <arnd@...nel.org>
Cc: "Luis Chamberlain" <mcgrof@...nel.org>, linux-modules@...r.kernel.org,
 "Rafael J . Wysocki" <rafael@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [v2] module: don't ignore sysfs_create_link() failures

On Sat, Mar 23, 2024, at 17:50, Greg Kroah-Hartman wrote:
> On Fri, Mar 22, 2024 at 06:39:11PM +0100, Arnd Bergmann wrote:
>> diff --git a/drivers/base/bus.c b/drivers/base/bus.c
>> index daee55c9b2d9..7ef75b60d331 100644
>> --- a/drivers/base/bus.c
>> +++ b/drivers/base/bus.c
>> @@ -674,7 +674,12 @@ int bus_add_driver(struct device_driver *drv)
>>  		if (error)
>>  			goto out_del_list;
>>  	}
>> -	module_add_driver(drv->owner, drv);
>> +	error = module_add_driver(drv->owner, drv);
>> +	if (error) {
>> +		printk(KERN_ERR "%s: failed to create module links for %s\n",
>> +			__func__, drv->name);
>> +		goto out_del_list;
>
> Don't we need to walk back the driver_attach() call here if this fails?

Yes, fixed now. There are still some other calls right after
it that print an error but don't cause bus_add_driver() to fail
though. We may want to add similar unwinding there, but that
feels like it should be a separate patch.

>>  
>>  	if (!mk)
>> -		return;
>> +		return 0;
>> +
>> +	ret = sysfs_create_link(&drv->p->kobj, &mk->kobj, "module");
>> +	if (ret && ret != -EEXIST)
>
> Why would EEXIST happen here?  How can this be called twice?
>

My impression was that the lack of error handling and the
comment was ab out a case where that might happen
intentionally. I've removed it now as I couldn't find any
evidence that this is really needed. I suppose we would
find out in testing if we do.

     Arnd