On Sun, 2018-06-17 at 10:36 -0700, Kees Cook wrote:
> On Sat, Jun 16, 2018 at 3:04 PM, Mihai Donțu wrote:
> > On Sun, 2018-06-17 at 00:01 +0300, Mihai Donțu wrote:
> > > While trying to adjust the keyboard backlight mode, I hit this BUG:
> > >
> > > Jun 16 22:16:07 mdontu-l kernel: usercopy: Kernel memory overwrite attempt detected to spans multiple pages (offset 0, size 4104)!
>
> CONFIG_HARDENED_USERCOPY_PAGESPAN=y is really only useful for
> debugging special cases. For now, I recommend leaving it disabled,
> since there are a lot of cases it still trips over.
>
> > I eventually sprinkled some printk-s and got this:
> >
> > 855 if (copy_from_user(buf, input, wblock->req_buf_size)) {
> > 856 dev_dbg(&wblock->dev.dev, "Copy %llu from user failed\n",
> > 857 wblock->req_buf_size);
> > 858 ret = -EFAULT;
> > 859 goto out_ioctl;
> > 860 }
>
> However, since you tracked this one down, I think this would be fixed
> by adjusting the handler_data allocation:
>
>
> diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
> index 8e3d0146ff8c..ea6bf98f197a 100644
> --- a/drivers/platform/x86/wmi.c
> +++ b/drivers/platform/x86/wmi.c
> @@ -918,8 +918,8 @@ static int wmi_dev_probe(struct device *dev)
> }
>
> count = get_order(wblock->req_buf_size);
> - wblock->handler_data = (void *)__get_free_pages(GFP_KERNEL,
> - count);
> + wblock->handler_data = (void *)
> + __get_free_pages(GFP_KERNEL | __GFP_COMP, count);
> if (!wblock->handler_data) {
> ret = -ENOMEM;
> goto probe_failure;
>
Your patch works OK for me, thank you. The libsmbios tool, however, not
so much. It appears to be behind latest developments.
# echo "+keyboard" >/sys/class/leds/dell\:\:kbd_backlight/start_triggers
is all that is needed today.
Regards,
> But in looking further, I don't know why this is using
> __get_free_pages() instead of kmalloc? In fact, there is a kfree() in
> the error path, which looks wrong:
>
> kfree(wblock->handler_data);
>
> I think this should just be converted to using kmalloc/kfree everywhere.
--
Mihai Donțu
