> -----Original Message----- > From: platform-driver-x86-owner@xxxxxxxxxxxxxxx [mailto:platform-driver-x86- > owner@xxxxxxxxxxxxxxx] On Behalf Of Mihai Don?u > Sent: Sunday, June 17, 2018 2:30 PM > To: Kees Cook > Cc: LKML; Darren Hart; Andy Shevchenko; Platform Driver > Subject: Re: wmi: usercopy: Kernel memory overwrite attempt detected to spans > multiple pages (offset 0, size 4104) > > 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 Please feel free to send a PR to augment libsmbios to prefer this sysfs interface if it's present over the direct communication path. > > 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
