[PATCH] usb: core: hcd: fix bug: application of sizeof to pointer

[PATCH] usb: core: hcd: fix bug: application of sizeof to pointer

[Guo Zhengkui]

Fix following error:
./drivers/usb/core/hcd.c:1284:38-44: ERROR:
application of sizeof to pointer.

Use sizeof(*vaddr) instead.

Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
---
 drivers/usb/core/hcd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 4d326ee12c36..996d5273cf60 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1281,7 +1281,7 @@ static int hcd_alloc_coherent(struct usb_bus *bus,
 		return -EFAULT;
 	}
 
-	vaddr = hcd_buffer_alloc(bus, size + sizeof(vaddr),
+	vaddr = hcd_buffer_alloc(bus, size + sizeof(*vaddr),
 				 mem_flags, dma_handle);
 	if (!vaddr)
 		return -ENOMEM;
-- 
2.20.1

Re: [PATCH] usb: core: hcd: fix bug: application of sizeof to pointer

[Greg Kroah-Hartman]

On Tue, Dec 07, 2021 at 09:53:47PM +0800, Guo Zhengkui wrote:
> Fix following error:
> ./drivers/usb/core/hcd.c:1284:38-44: ERROR:
> application of sizeof to pointer.

What generated this error?

> 
> Use sizeof(*vaddr) instead.
> 
> Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
> ---
>  drivers/usb/core/hcd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> index 4d326ee12c36..996d5273cf60 100644
> --- a/drivers/usb/core/hcd.c
> +++ b/drivers/usb/core/hcd.c
> @@ -1281,7 +1281,7 @@ static int hcd_alloc_coherent(struct usb_bus *bus,
>  		return -EFAULT;
>  	}
>  
> -	vaddr = hcd_buffer_alloc(bus, size + sizeof(vaddr),
> +	vaddr = hcd_buffer_alloc(bus, size + sizeof(*vaddr),

I think you just broke the code.

Look at this closer and see what the function is doing with this buffer
and if you still think your patch is correct, please rewrite the
changelog text to explain why it is so (hint, just using the output of
coccinelle isn't ok.)

thanks,

greg k-h

Re: [PATCH] usb: core: hcd: fix bug: application of sizeof to pointer

[Alan Stern]

On Tue, Dec 07, 2021 at 03:40:37PM +0100, Greg Kroah-Hartman wrote:
> On Tue, Dec 07, 2021 at 09:53:47PM +0800, Guo Zhengkui wrote:
> > Fix following error:
> > ./drivers/usb/core/hcd.c:1284:38-44: ERROR:
> > application of sizeof to pointer.
> 
> What generated this error?
> 
> > 
> > Use sizeof(*vaddr) instead.
> > 
> > Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
> > ---
> >  drivers/usb/core/hcd.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> > index 4d326ee12c36..996d5273cf60 100644
> > --- a/drivers/usb/core/hcd.c
> > +++ b/drivers/usb/core/hcd.c
> > @@ -1281,7 +1281,7 @@ static int hcd_alloc_coherent(struct usb_bus *bus,
> >  		return -EFAULT;
> >  	}
> >  
> > -	vaddr = hcd_buffer_alloc(bus, size + sizeof(vaddr),
> > +	vaddr = hcd_buffer_alloc(bus, size + sizeof(*vaddr),
> 
> I think you just broke the code.
> 
> Look at this closer and see what the function is doing with this buffer
> and if you still think your patch is correct, please rewrite the
> changelog text to explain why it is so (hint, just using the output of
> coccinelle isn't ok.)

Although the patch is definitely wrong, the code could stand to be 
improved.  The value stored at the end of the buffer is *vaddr_handle 
converted to an unsigned long, but the space reserved for this value is 
sizeof(vaddr) -- which doesn't make much sense since vaddr is a pointer 
to unsigned char.  The code implicitly relies on the fact that unsigned 
long takes up the same amount of space as a pointer.

Readers wouldn't have to stop and figure this out if the amount of 
reserved space was simply set to sizeof(unsigned long) rather than 
sizeof(vaddr).

Alan Stern

Re: [PATCH] usb: core: hcd: fix bug: application of sizeof to pointer

[Guo Zhengkui]

On 2021/12/8 6:21, Alan Stern wrote:
> On Tue, Dec 07, 2021 at 03:40:37PM +0100, Greg Kroah-Hartman wrote:
>> On Tue, Dec 07, 2021 at 09:53:47PM +0800, Guo Zhengkui wrote:
>>> Fix following error:
>>> ./drivers/usb/core/hcd.c:1284:38-44: ERROR:
>>> application of sizeof to pointer.
>>
>> What generated this error?
>>
>>>
>>> Use sizeof(*vaddr) instead.
>>>
>>> Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
>>> ---
>>>   drivers/usb/core/hcd.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
>>> index 4d326ee12c36..996d5273cf60 100644
>>> --- a/drivers/usb/core/hcd.c
>>> +++ b/drivers/usb/core/hcd.c
>>> @@ -1281,7 +1281,7 @@ static int hcd_alloc_coherent(struct usb_bus *bus,
>>>   		return -EFAULT;
>>>   	}
>>>   
>>> -	vaddr = hcd_buffer_alloc(bus, size + sizeof(vaddr),
>>> +	vaddr = hcd_buffer_alloc(bus, size + sizeof(*vaddr),
>>
>> I think you just broke the code.
>>
>> Look at this closer and see what the function is doing with this buffer
>> and if you still think your patch is correct, please rewrite the
>> changelog text to explain why it is so (hint, just using the output of
>> coccinelle isn't ok.)
> 

Sorry for my carelessness. It should be sizeof(vaddr).

> Although the patch is definitely wrong, the code could stand to be
> improved.  The value stored at the end of the buffer is *vaddr_handle
> converted to an unsigned long, but the space reserved for this value is
> sizeof(vaddr) -- which doesn't make much sense since vaddr is a pointer
> to unsigned char.  The code implicitly relies on the fact that unsigned
> long takes up the same amount of space as a pointer.
> 
> Readers wouldn't have to stop and figure this out if the amount of
> reserved space was simply set to sizeof(unsigned long) rather than
> sizeof(vaddr).

OK, I will commit another patch to fix this problem. Do you mind I add a 
"Suggested-by" tag of your name (Alan Stern) in this new patch?

Zhengkui

> 
> Alan Stern
> 

Re: [PATCH] usb: core: hcd: fix bug: application of sizeof to pointer

[Greg Kroah-Hartman]

On Tue, Dec 07, 2021 at 05:21:05PM -0500, Alan Stern wrote:
> On Tue, Dec 07, 2021 at 03:40:37PM +0100, Greg Kroah-Hartman wrote:
> > On Tue, Dec 07, 2021 at 09:53:47PM +0800, Guo Zhengkui wrote:
> > > Fix following error:
> > > ./drivers/usb/core/hcd.c:1284:38-44: ERROR:
> > > application of sizeof to pointer.
> > 
> > What generated this error?
> > 
> > > 
> > > Use sizeof(*vaddr) instead.
> > > 
> > > Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
> > > ---
> > >  drivers/usb/core/hcd.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> > > index 4d326ee12c36..996d5273cf60 100644
> > > --- a/drivers/usb/core/hcd.c
> > > +++ b/drivers/usb/core/hcd.c
> > > @@ -1281,7 +1281,7 @@ static int hcd_alloc_coherent(struct usb_bus *bus,
> > >  		return -EFAULT;
> > >  	}
> > >  
> > > -	vaddr = hcd_buffer_alloc(bus, size + sizeof(vaddr),
> > > +	vaddr = hcd_buffer_alloc(bus, size + sizeof(*vaddr),
> > 
> > I think you just broke the code.
> > 
> > Look at this closer and see what the function is doing with this buffer
> > and if you still think your patch is correct, please rewrite the
> > changelog text to explain why it is so (hint, just using the output of
> > coccinelle isn't ok.)
> 
> Although the patch is definitely wrong, the code could stand to be 
> improved.  The value stored at the end of the buffer is *vaddr_handle 
> converted to an unsigned long, but the space reserved for this value is 
> sizeof(vaddr) -- which doesn't make much sense since vaddr is a pointer 
> to unsigned char.  The code implicitly relies on the fact that unsigned 
> long takes up the same amount of space as a pointer.

Linux requires that an unsigned long is the same size as a pointer, so
this is not a new requirement that is unique to this function :)

thanks,

greg k-h

Re: [PATCH] usb: core: hcd: fix bug: application of sizeof to pointer

[Alan Stern]

On Wed, Dec 08, 2021 at 11:00:41AM +0800, Guo Zhengkui wrote:
> On 2021/12/8 6:21, Alan Stern wrote:
> > On Tue, Dec 07, 2021 at 03:40:37PM +0100, Greg Kroah-Hartman wrote:
> > > On Tue, Dec 07, 2021 at 09:53:47PM +0800, Guo Zhengkui wrote:
> > > > Fix following error:
> > > > ./drivers/usb/core/hcd.c:1284:38-44: ERROR:
> > > > application of sizeof to pointer.
> > > 
> > > What generated this error?
> > > 
> > > > 
> > > > Use sizeof(*vaddr) instead.
> > > > 
> > > > Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
> > > > ---
> > > >   drivers/usb/core/hcd.c | 2 +-
> > > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> > > > index 4d326ee12c36..996d5273cf60 100644
> > > > --- a/drivers/usb/core/hcd.c
> > > > +++ b/drivers/usb/core/hcd.c
> > > > @@ -1281,7 +1281,7 @@ static int hcd_alloc_coherent(struct usb_bus *bus,
> > > >   		return -EFAULT;
> > > >   	}
> > > > -	vaddr = hcd_buffer_alloc(bus, size + sizeof(vaddr),
> > > > +	vaddr = hcd_buffer_alloc(bus, size + sizeof(*vaddr),
> > > 
> > > I think you just broke the code.
> > > 
> > > Look at this closer and see what the function is doing with this buffer
> > > and if you still think your patch is correct, please rewrite the
> > > changelog text to explain why it is so (hint, just using the output of
> > > coccinelle isn't ok.)
> > 
> 
> Sorry for my carelessness. It should be sizeof(vaddr).
> 
> > Although the patch is definitely wrong, the code could stand to be
> > improved.  The value stored at the end of the buffer is *vaddr_handle
> > converted to an unsigned long, but the space reserved for this value is
> > sizeof(vaddr) -- which doesn't make much sense since vaddr is a pointer
> > to unsigned char.  The code implicitly relies on the fact that unsigned
> > long takes up the same amount of space as a pointer.
> > 
> > Readers wouldn't have to stop and figure this out if the amount of
> > reserved space was simply set to sizeof(unsigned long) rather than
> > sizeof(vaddr).
> 
> OK, I will commit another patch to fix this problem. Do you mind I add a
> "Suggested-by" tag of your name (Alan Stern) in this new patch?

That's fine.

Alan Stern

[PATCH] usb: core: hcd: change sizeof(vaddr) to sizeof(unsigned long)

[Guo Zhengkui]

`vaddr` is a pointer to unsigned char. sizeof(vaddr) here intends
to get the size of a pointer. But readers may get confused. Change
sizeof(vaddr) to sizeof(unsigned long) makes more sense.

Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
---
 drivers/usb/core/hcd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 4d326ee12c36..9ffc63ae65ac 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1281,7 +1281,7 @@ static int hcd_alloc_coherent(struct usb_bus *bus,
 		return -EFAULT;
 	}
 
-	vaddr = hcd_buffer_alloc(bus, size + sizeof(vaddr),
+	vaddr = hcd_buffer_alloc(bus, size + sizeof(unsigned long),
 				 mem_flags, dma_handle);
 	if (!vaddr)
 		return -ENOMEM;
-- 
2.20.1