AW: KASAN: use-after-free Read in usbhid_power

["Schmid, Carsten" <Carsten_Schmid@mentor.com>]

Hi all having use-after-free issues in USB shutdowns:
I hunted for a similar case in the intel_xhci_usb_sw driver.
What i have found and proposed is (from yesterday):
---
[PATCH] kernel/resource.c: invalidate parent when freed resource has childs

When a resource is freed and has children, the childrens are
left without any hint that their parent is no more valid.
This caused at least one use-after-free in the xhci-hcd using
ext-caps driver when platform code released platform devices.

Fix this by setting child's parent to zero and warn.

Signed-off-by: Carsten Schmid <carsten_schmid@mentor.com>
---
Rationale:
When hunting for the root cause of a crash on a 4.14.86 kernel, i
have found the root cause and checked it being still present
upstream. Our case:
Having xhci-hcd and intel_xhci_usb_sw active we can see in
/proc/meminfo: (exceirpt)
  b3c00000-b3c0ffff : 0000:00:15.0
    b3c00000-b3c0ffff : xhci-hcd
      b3c08070-b3c0846f : intel_xhci_usb_sw
intel_xhci_usb_sw being a child of xhci-hcd.

Doing an unbind command
echo 0000:00:15.0 > /sys/bus/pci/drivers/xhci_hcd/unbind
leads to xhci-hcd being freed in __release_region.
The intel_xhci_usb_sw resource is accessed in platform code
in platform_device_del with
                for (i = 0; i < pdev->num_resources; i++) {
                        struct resource *r = &pdev->resource[i];
                        if (r->parent)
                                release_resource(r);
                }
as the resource's parent has not been updated, the release_resource
uses the parent:
        p = &old->parent->child;
which is now invalid.
Fix this by marking the parent invalid in the child and give a warning
in dmesg.
---
 kernel/resource.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/resource.c b/kernel/resource.c
index 158f04ec1d4f..95340cb0b1c2 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1200,6 +1200,15 @@ void __release_region(struct resource *parent, resource_size_t start,
                        write_unlock(&resource_lock);
                        if (res->flags & IORESOURCE_MUXED)
                                wake_up(&muxed_resource_wait);
+
+                       write_lock(&resource_lock);
+                       if (res->child) {
+                               printk(KERN_WARNING "__release_region: %s has child %s,"
+                                               "invalidating childs parent\n",
+                                               res->name, res->child->name);
+                               res->child->parent = NULL;
+                       }
+                       write_unlock(&resource_lock);
                        free_resource(res);
                        return;
                }
--
2.17.1

> -----Ursprüngliche Nachricht-----
> Von: linux-usb-owner@vger.kernel.org [mailto:linux-usb-
> owner@vger.kernel.org] Im Auftrag von Alan Stern
> Gesendet: Donnerstag, 8. August 2019 21:37
> An: Andrey Konovalov <andreyknvl@google.com>
> Cc: Oliver Neukum <oneukum@suse.com>; syzkaller-bugs <syzkaller-
> bugs@googlegroups.com>; syzbot
> <syzbot+ef5de9c4f99c4edb4e49@syzkaller.appspotmail.com>; USB list
> <linux-usb@vger.kernel.org>; Hillf Danton <hdanton@sina.com>
> Betreff: Re: KASAN: use-after-free Read in usbhid_power
> 
> On Thu, 8 Aug 2019, Andrey Konovalov wrote:
> 
> > On Thu, Jul 25, 2019 at 5:09 PM Alan Stern <stern@rowland.harvard.edu>
> wrote:
> > >
> > > On Thu, 25 Jul 2019, Oliver Neukum wrote:
> > >
> > > > Am Mittwoch, den 24.07.2019, 17:02 -0400 schrieb Alan Stern:
> > > > > On Wed, 24 Jul 2019, Oliver Neukum wrote:
> > > > >
> > > > > >  drivers/hid/usbhid/hid-core.c | 13 +++++++++++++
> > > > > >  1 file changed, 13 insertions(+)
> > > > > >
> > > > > > diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-
> core.c
> > > > > > index c7bc9db5b192..98b996ecf4d3 100644
> > > > > > --- a/drivers/hid/usbhid/hid-core.c
> > > > > > +++ b/drivers/hid/usbhid/hid-core.c
> > > > > > @@ -1229,6 +1229,17 @@ static int usbhid_power(struct hid_device
> *hid, int lvl)
> > > > > >   struct usbhid_device *usbhid = hid->driver_data;
> > > > > >   int r = 0;
> > > > > >
> > > > > > + spin_lock_irq(&usbhid->lock);
> > > > > > + if (test_bit(HID_DISCONNECTED, &usbhid->iofl)) {
> > > > > > +         r = -ENODEV;
> > > > > > +         spin_unlock_irq(&usbhid->lock);
> > > > > > +         goto bail_out;
> > > > > > + } else {
> > > > > > +         /* protect against disconnect */
> > > > > > +         usb_get_dev(interface_to_usbdev(usbhid->intf));
> > > > > > +         spin_unlock_irq(&usbhid->lock);
> > > > > > + }
> > > > > > +
> > > > > >   switch (lvl) {
> > > > > >   case PM_HINT_FULLON:
> > > > > >           r = usb_autopm_get_interface(usbhid->intf);
> > > > > > @@ -1238,7 +1249,9 @@ static int usbhid_power(struct hid_device
> *hid, int lvl)
> > > > > >           usb_autopm_put_interface(usbhid->intf);
> > > > > >           break;
> > > > > >   }
> > > > > > + usb_put_dev(interface_to_usbdev(usbhid->intf));
> > > > > >
> > > > > > +bail_out:
> > > > > >   return r;
> > > > > >  }
> 
> > This report looks like very similar to these two:
> >
> > https://syzkaller.appspot.com/bug?extid=b156665cf4d1b5e00c76
> > https://syzkaller.appspot.com/bug?extid=3cbe5cd105d2ad56a1df
> 
> It also seems to resemble extids a7a6b9c609b9457c62c6,
> 62a1e04fd3ec2abf099e, and 75e6910bf03e266a277f, although this may be an
> illusion.
> 
> > Maybe we should mark those two as duplicates.
> >
> > Hillf suggested a fix on one of them, but it looks different from what
> > you propose:
> >
> > https://groups.google.com/d/msg/syzkaller-
> bugs/xW7LvKfpyn0/SpKbs5ZLEAAJ
> 
> Go ahead and try it out on all of them.  I don't have a clear feeling
> about it, not having worked on usbhid in quite a while.
> 
> Alan Stern