On Wed, 24 Jul 2019, Oliver Neukum wrote: > Am Dienstag, den 23.07.2019, 05:48 -0700 schrieb syzbot: > > Hello, > > > > syzbot found the following crash on: > > > > HEAD commit: 6a3599ce usb-fuzzer: main usb gadget fuzzer driver > > git tree: https://github.com/google/kasan.git usb-fuzzer > > console output: https://syzkaller.appspot.com/x/log.txt?x=11b13e78600000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=700ca426ab83faae > > dashboard link: https://syzkaller.appspot.com/bug?extid=ef5de9c4f99c4edb4e49 > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15482210600000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1139b07c600000 > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+ef5de9c4f99c4edb4e49@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > ================================================================== > > BUG: KASAN: use-after-free in usbhid_power+0xca/0xe0 > > /drivers/hid/usbhid/hid-core.c:1234 > > Read of size 8 at addr ffff8881ce8a4008 by task syz-executor373/1763 > > #syz test: https://github.com/google/kasan.git usb-fuzzer > > From a3455c4527bdfe86536856ea96288b7dcc36590b Mon Sep 17 00:00:00 2001 > From: Oliver Neukum <oneukum@xxxxxxxx> > Date: Wed, 24 Jul 2019 22:49:57 +0200 > Subject: [PATCH] usbhid: test for disconnected state in raw opening > > If the device has been disconnected, we should not proceed to use > runtime PM on it. > > Reported-by: syzbot+ef5de9c4f99c4edb4e49@xxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Oliver Neukum <oneukum@xxxxxxx> > --- > 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; > } Isn't this treating the symptom instead of the cause? Shouldn't the hid_device hold a reference to usbhid->intf throughout its lifetime? That way this sort of problem wouldn't arise in any routine, not just usbhid_power(). Alan Stern
