linux-kernel - Re: [PATCH v3] mwifiex: fix sleep in atomic context bugs caused by dev

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Date:   Mon, 23 May 2022 14:31:48 +0300
From:   Kalle Valo <kvalo@...nel.org>
To:     duoming@....edu.cn
Cc:     "Greg KH" <gregkh@...uxfoundation.org>,
        linux-wireless@...r.kernel.org, amitkarwar@...il.com,
        ganapathi017@...il.com, sharvari.harisangam@....com,
        huxinming820@...il.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, rafael@...nel.org,
        Johannes Berg <johannes@...solutions.net>
Subject: Re: [PATCH v3] mwifiex: fix sleep in atomic context bugs caused by dev_coredumpv

(adding Johannes)

duoming@....edu.cn writes:

>> > --- a/lib/kobject.c
>> > +++ b/lib/kobject.c
>> > @@ -254,7 +254,7 @@ int kobject_set_name_vargs(struct kobject *kobj, const char *fmt,
>> >  	if (kobj->name && !fmt)
>> >  		return 0;
>> >  
>> > -	s = kvasprintf_const(GFP_KERNEL, fmt, vargs);
>> > +	s = kvasprintf_const(GFP_ATOMIC, fmt, vargs);
>> >  	if (!s)
>> >  		return -ENOMEM;
>> >  
>> > @@ -267,7 +267,7 @@ int kobject_set_name_vargs(struct kobject *kobj, const char *fmt,
>> >  	if (strchr(s, '/')) {
>> >  		char *t;
>> >  
>> > -		t = kstrdup(s, GFP_KERNEL);
>> > +		t = kstrdup(s, GFP_ATOMIC);
>> >  		kfree_const(s);
>> >  		if (!t)
>> >  			return -ENOMEM;
>> 
>> Please no, you are hurting the whole kernel because of one odd user.
>> Please do not make these calls under atomic context.
>
> Thanks for your time and suggestions. I will remove the gfp_t
> parameter of dev_coredumpv in order to show it could not be used in
> atomic context.

In a way it would be nice to be able to call dev_coredump from atomic
contexts, though I don't know how practical it actually is. Is there any
other option? What about adding a gfp_t parameter to dev_set_name()? Or
is there an alternative for dev_set_name() which can be called in atomic
contexts?

Johannes&Greg, any ideas?

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