On Tue, 17 Jul 2018, Greg KH wrote:
> > From: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx>
> > Date: Tue, 10 Jul 2018 09:50:00 +0100
> > Subject: [PATCH] hacky solution to mem-corruption
> >
> > Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx>
> > ---
> > drivers/usb/core/message.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
> > index 7cd4ec33dbf4..7fdf7a27611d 100644
> > --- a/drivers/usb/core/message.c
> > +++ b/drivers/usb/core/message.c
> > @@ -1398,7 +1398,8 @@ int usb_set_interface(struct usb_device *dev, int interface, int alternate)
> > remove_intf_ep_devs(iface);
> > usb_remove_sysfs_intf_files(iface);
> > }
> > - usb_disable_interface(dev, iface, true);
> > + if (!(iface->cur_altsetting && alt))
> > + usb_disable_interface(dev, iface, true);
>
>
>
> This feels like a "correct" patch anyway, why would a driver keep
> calling set_interface to an interface that it was already set to?
>
> But can't we check for this higher up in the function? This hack will
> just not disable an interface but it will do all of the other stuff
> being asked for. Does the patch below also solve this for you? It's
> not a good solution of course, but it might work around the problem a
> bit better.
>
> thanks,
>
> greg k-h
>
> diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
> index 1a15392326fc..0f718f1a1ca3 100644
> --- a/drivers/usb/core/message.c
> +++ b/drivers/usb/core/message.c
> @@ -1376,6 +1376,14 @@ int usb_set_interface(struct usb_device *dev, int interface, int alternate)
> return -EINVAL;
> }
>
> + if (iface->cur_altsetting == alt) {
> + /*
> + * foolish bluetooth stack, don't try to set a setting you are
> + * already set to...
> + */
> + return 0;
> + }
> +
> /* Make sure we have enough bandwidth for this alternate interface.
> * Remove the current alt setting and add the new alt setting.
> */
No, neither of these is right. It's possible to use
usb_set_interface() as a kind of "soft" reset. Even when the new
altsetting is specified to be the same as the current one, we still
have to tell the lower-layer drivers and hardware about it.
Alan Stern
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