Re: [PATCH next] driver core: Replace strcpy() with memcpy()

["Danilo Krummrich" <dakr@kernel.org>]

On Tue Jun 9, 2026 at 5:22 PM CEST, David Laight wrote:
> On Tue, 09 Jun 2026 16:08:55 +0200
> "Danilo Krummrich" <dakr@kernel.org> wrote:
>
>> On Sat Jun 6, 2026 at 10:25 PM CEST, david.laight.linux wrote:
>> > diff --git a/drivers/base/platform.c b/drivers/base/platform.c
>> > index 75b4698d0e58..63fdfffe1a8c 100644
>> > --- a/drivers/base/platform.c
>> > +++ b/drivers/base/platform.c
>> > @@ -617,10 +617,11 @@ static void platform_device_release(struct device *dev)
>> >  struct platform_device *platform_device_alloc(const char *name, int id)
>> >  {
>> >  	struct platform_object *pa;
>> > +	size_t len = strlen(name);  
>> 
>> This could be strlen(name) + 1 right away, which would also avoid the memcpy()
>> to implicitly rely on kzalloc() zeroing the memory, where strcpy() was
>> self-contained before.
>
> I tried not to do that 'optimisation'.
> Here the kzalloc() is almost certainly needed for other reasons.

This is true, it is needed for other reasons anyway. My point is that currently
it is self-contained and it doesn't matter if the preconditions ever change, so
I'd rather we have strlen(name) + 1 right away.

> There is also the issue that, in principle (but probably not in practise),
> the input string might change between the strlen() and the copy.

This is not a concern for this function, but let's assume it was, then your
proposed patch wouldn't prevent anything bad either.

For instance, if the string would change to be shorter than what strlen()
measured, the memcpy() becomes invalid either way.

Also, in that case the strcpy() would be more robust and vice versa with a
longer one. But again, this is not a realistic scenario anyway.

> So it is probably best practise to not rely on the '\0' still being
> there when the copy is done.
>
>> 
>> >  
>> > -	pa = kzalloc(sizeof(*pa) + strlen(name) + 1, GFP_KERNEL);
>> > +	pa = kzalloc(sizeof(*pa) + len + 1, GFP_KERNEL);
>> >  	if (pa) {
>> > -		strcpy(pa->name, name);
>> > +		memcpy(pa->name, name, len);  
>> 
>> But in general, what's the improvement? strlen() still operates on a potentially
>> unbounded string?
>> 
>> It removes the redundant strlen() calculation that is implied by the current
>> code, though this may be eliminated by CSE optimization.
>
> CSE won't eliminate it.

Ok, but in the context of platform_device_alloc() not a huge benefit either.

Is there any other reason for this change? Am I missing something?