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@xxxxxxxxxx>
---
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@xxxxxxxxxxxxxxx [mailto:linux-usb-
> owner@xxxxxxxxxxxxxxx] Im Auftrag von Alan Stern
> Gesendet: Donnerstag, 8. August 2019 21:37
> An: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> Cc: Oliver Neukum <oneukum@xxxxxxxx>; syzkaller-bugs <syzkaller-
> bugs@xxxxxxxxxxxxxxxx>; syzbot
> <syzbot+ef5de9c4f99c4edb4e49@xxxxxxxxxxxxxxxxxxxxxxxxx>; USB list
> <linux-usb@xxxxxxxxxxxxxxx>; Hillf Danton <hdanton@xxxxxxxx>
> 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@xxxxxxxxxxxxxxxxxxx>
> 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
