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

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