There will be 2 leading bytes indicating the total length of
the PNP string, so I think we should add value by 2, otherwise
the PNP string copied to user will not contain the last 2 bytes
Signed-off-by: Wei Ming Chen <[email protected]>
---
drivers/usb/gadget/function/f_printer.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
index abec5c58f525..3fb00fd0b5ee 100644
--- a/drivers/usb/gadget/function/f_printer.c
+++ b/drivers/usb/gadget/function/f_printer.c
@@ -1005,9 +1005,11 @@ static int printer_func_setup(struct usb_function *f,
break;
}
value = strlen(dev->pnp_string);
+ memcpy(buf + 2, dev->pnp_string, value);
+
+ value += 2;
buf[0] = (value >> 8) & 0xFF;
buf[1] = value & 0xFF;
- memcpy(buf + 2, dev->pnp_string, value);
DBG(dev, "1284 PNP String: %x %s\n", value,
dev->pnp_string);
break;
--
2.25.1
On Wed, Jan 05, 2022 at 12:04:39PM +0800, Wei Ming Chen wrote:
> There will be 2 leading bytes indicating the total length of
> the PNP string, so I think we should add value by 2, otherwise
> the PNP string copied to user will not contain the last 2 bytes
>
> Signed-off-by: Wei Ming Chen <[email protected]>
> ---
> drivers/usb/gadget/function/f_printer.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
> index abec5c58f525..3fb00fd0b5ee 100644
> --- a/drivers/usb/gadget/function/f_printer.c
> +++ b/drivers/usb/gadget/function/f_printer.c
> @@ -1005,9 +1005,11 @@ static int printer_func_setup(struct usb_function *f,
> break;
> }
> value = strlen(dev->pnp_string);
> + memcpy(buf + 2, dev->pnp_string, value);
> +
> + value += 2;
> buf[0] = (value >> 8) & 0xFF;
> buf[1] = value & 0xFF;
> - memcpy(buf + 2, dev->pnp_string, value);
> DBG(dev, "1284 PNP String: %x %s\n", value,
> dev->pnp_string);
> break;
> --
> 2.25.1
>
Are you sure this is correct?
How is this related to this recent thread:
https://lore.kernel.org/all/CAKjGFBUdjXcZoVV4jdrgTz4rKThTfZAK4CqreKmBZ4KHE+K1GA@mail.gmail.com/#t
your change is different from what is proposed there, why?
thanks,
greg k-h
Greg KH <[email protected]> 於 2022年1月6日 週四 下午10:35寫道：
>
> On Wed, Jan 05, 2022 at 12:04:39PM +0800, Wei Ming Chen wrote:
> > There will be 2 leading bytes indicating the total length of
> > the PNP string, so I think we should add value by 2, otherwise
> > the PNP string copied to user will not contain the last 2 bytes
> >
> > Signed-off-by: Wei Ming Chen <[email protected]>
> > ---
> > drivers/usb/gadget/function/f_printer.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
> > index abec5c58f525..3fb00fd0b5ee 100644
> > --- a/drivers/usb/gadget/function/f_printer.c
> > +++ b/drivers/usb/gadget/function/f_printer.c
> > @@ -1005,9 +1005,11 @@ static int printer_func_setup(struct usb_function *f,
> > break;
> > }
> > value = strlen(dev->pnp_string);
> > + memcpy(buf + 2, dev->pnp_string, value);
> > +
> > + value += 2;
> > buf[0] = (value >> 8) & 0xFF;
> > buf[1] = value & 0xFF;
> > - memcpy(buf + 2, dev->pnp_string, value);
> > DBG(dev, "1284 PNP String: %x %s\n", value,
> > dev->pnp_string);
> > break;
> > --
> > 2.25.1
> >
>
> Are you sure this is correct?
>
> How is this related to this recent thread:
> https://lore.kernel.org/all/CAKjGFBUdjXcZoVV4jdrgTz4rKThTfZAK4CqreKmBZ4KHE+K1GA@mail.gmail.com/#t
>
> your change is different from what is proposed there, why?
I didn’t notice this thread before I send this patch, I think the
concept of my change is similar to Volodymyr Lisivka’s change, he/she
introduced a separate variable for the PNP string length, I think it
may be clearer and more readable than just “value += 2”
Another thing that I am not too sure whether I am correct is this line of code
DBG(dev, "1284 PNP String: %x %s\n", value,
dev->pnp_string);
What Volodymyr Lisivka changed is like this
DBG(dev, "1284 PNP String: %x %s\n", pnp_length,
dev->pnp_string);
In my change, “value” equals to “pnp_length + 2” in Volodymyr
Lisivka’s change, and I think we should print “the PNP string length +
2” instead of “the PNP string length”?
>
> thanks,
>
> greg k-h
thanks,
Wei Ming Chen
On Fri, Jan 07, 2022 at 10:37:19AM +0800, 陳偉銘 wrote:
> Greg KH <[email protected]> 於 2022年1月6日 週四 下午10:35寫道：
> >
> > On Wed, Jan 05, 2022 at 12:04:39PM +0800, Wei Ming Chen wrote:
> > > There will be 2 leading bytes indicating the total length of
> > > the PNP string, so I think we should add value by 2, otherwise
> > > the PNP string copied to user will not contain the last 2 bytes
> > >
> > > Signed-off-by: Wei Ming Chen <[email protected]>
> > > ---
> > > drivers/usb/gadget/function/f_printer.c | 4 +++-
> > > 1 file changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
> > > index abec5c58f525..3fb00fd0b5ee 100644
> > > --- a/drivers/usb/gadget/function/f_printer.c
> > > +++ b/drivers/usb/gadget/function/f_printer.c
> > > @@ -1005,9 +1005,11 @@ static int printer_func_setup(struct usb_function *f,
> > > break;
> > > }
> > > value = strlen(dev->pnp_string);
> > > + memcpy(buf + 2, dev->pnp_string, value);
> > > +
> > > + value += 2;
> > > buf[0] = (value >> 8) & 0xFF;
> > > buf[1] = value & 0xFF;
> > > - memcpy(buf + 2, dev->pnp_string, value);
> > > DBG(dev, "1284 PNP String: %x %s\n", value,
> > > dev->pnp_string);
> > > break;
> > > --
> > > 2.25.1
> > >
> >
> > Are you sure this is correct?
> >
> > How is this related to this recent thread:
> > https://lore.kernel.org/all/CAKjGFBUdjXcZoVV4jdrgTz4rKThTfZAK4CqreKmBZ4KHE+K1GA@mail.gmail.com/#t
> >
> > your change is different from what is proposed there, why?
>
> I didn’t notice this thread before I send this patch, I think the
> concept of my change is similar to Volodymyr Lisivka’s change, he/she
> introduced a separate variable for the PNP string length, I think it
> may be clearer and more readable than just “value += 2”
>
>
> Another thing that I am not too sure whether I am correct is this line of code
>
> DBG(dev, "1284 PNP String: %x %s\n", value,
> dev->pnp_string);
>
> What Volodymyr Lisivka changed is like this
>
> DBG(dev, "1284 PNP String: %x %s\n", pnp_length,
> dev->pnp_string);
>
> In my change, “value” equals to “pnp_length + 2” in Volodymyr
> Lisivka’s change, and I think we should print “the PNP string length +
> 2” instead of “the PNP string length”?
>
I do not know, I suggest you two work together to get the correct fix
submitted.
thanks,
greg k-h