Re: KASAN: slab-out-of-bounds Write in ga_probe

[Alan Stern]

On Thu, 19 Sep 2019, Andrey Konovalov wrote:

> On Tue, Sep 17, 2019 at 8:24 PM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> >
> > On Mon, 16 Sep 2019, syzbot wrote:
> >
> > > Hello,
> > >
> > > syzbot found the following crash on:
> > >
> > > HEAD commit:    f0df5c1b 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=14045831600000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=403741a091bf41d4ae79
> > > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13c1e62d600000
> > > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=166a3a95600000
> > >
> > > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > > Reported-by: syzbot+403741a091bf41d4ae79@xxxxxxxxxxxxxxxxxxxxxxxxx
> > >
> > > usb 1-1: config 0 interface 0 altsetting 0 has 1 endpoint descriptor,
> > > different from the interface descriptor's value: 9
> > > usb 1-1: New USB device found, idVendor=0e8f, idProduct=0012, bcdDevice=
> > > 0.00
> > > usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
> > > usb 1-1: config 0 descriptor??
> > > greenasia 0003:0E8F:0012.0001: unknown main item tag 0x0
> > > greenasia 0003:0E8F:0012.0001: hidraw0: USB HID v0.00 Device [HID
> > > 0e8f:0012] on usb-dummy_hcd.0-1/input0
> > > ==================================================================
> > > BUG: KASAN: slab-out-of-bounds in set_bit
> > > include/asm-generic/bitops-instrumented.h:28 [inline]
> > > BUG: KASAN: slab-out-of-bounds in gaff_init drivers/hid/hid-gaff.c:97
> > > [inline]
> > > BUG: KASAN: slab-out-of-bounds in ga_probe+0x1fd/0x6f0
> > > drivers/hid/hid-gaff.c:146
> > > Write of size 8 at addr ffff8881d9acafc0 by task kworker/1:1/78
> > >
> > > CPU: 1 PID: 78 Comm: kworker/1:1 Not tainted 5.3.0-rc7+ #0
> > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > > Google 01/01/2011
> > > Workqueue: usb_hub_wq hub_event
> > > Call Trace:
> > >   __dump_stack lib/dump_stack.c:77 [inline]
> > >   dump_stack+0xca/0x13e lib/dump_stack.c:113
> > >   print_address_description+0x6a/0x32c mm/kasan/report.c:351
> > >   __kasan_report.cold+0x1a/0x33 mm/kasan/report.c:482
> > >   kasan_report+0xe/0x12 mm/kasan/common.c:618
> > >   check_memory_region_inline mm/kasan/generic.c:185 [inline]
> > >   check_memory_region+0x128/0x190 mm/kasan/generic.c:192
> > >   set_bit include/asm-generic/bitops-instrumented.h:28 [inline]
> > >   gaff_init drivers/hid/hid-gaff.c:97 [inline]
> > >   ga_probe+0x1fd/0x6f0 drivers/hid/hid-gaff.c:146
> > >   hid_device_probe+0x2be/0x3f0 drivers/hid/hid-core.c:2209
> > >   really_probe+0x281/0x6d0 drivers/base/dd.c:548
> > >   driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
> > >   __device_attach_driver+0x
> > >
> > >
> > > ---
> > > This bug is generated by a bot. It may contain errors.
> > > See https://goo.gl/tpsmEJ for more information about syzbot.
> > > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx
> > >
> > > syzbot will keep track of this bug report. See:
> > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > > syzbot can test patches for this bug, for details see:
> > > https://goo.gl/tpsmEJ#testing-patches
> >
> > The driver assumes that the device contains an input.
> 
> BTW, these two reports look fairly similar:
> 
> https://syzkaller.appspot.com/bug?extid=94e2b9e9c7d1dd332345
> https://syzkaller.appspot.com/bug?extid=1e86e2ccce227cca899b

Indeed they do.  I don't have time to patch them now; maybe next week.
Unless you or someone else would like to do it first...  :-)  

Essentially the same fix should work for each of these -- looks like
they were written using copy-and-paste.  In fact, a quick grep through
drivers/hid/*.c shows about 9 of them with the same suspect
initialization code for hidinput.

Alan Stern          


> >  drivers/hid/hid-gaff.c |   12 +++++++++---
> >  1 file changed, 9 insertions(+), 3 deletions(-)
> >
> > Index: usb-devel/drivers/hid/hid-gaff.c
> > ===================================================================
> > --- usb-devel.orig/drivers/hid/hid-gaff.c
> > +++ usb-devel/drivers/hid/hid-gaff.c
> > @@ -64,14 +64,20 @@ static int gaff_init(struct hid_device *
> >  {
> >         struct gaff_device *gaff;
> >         struct hid_report *report;
> > -       struct hid_input *hidinput = list_entry(hid->inputs.next,
> > -                                               struct hid_input, list);
> > +       struct hid_input *hidinput;
> >         struct list_head *report_list =
> >                         &hid->report_enum[HID_OUTPUT_REPORT].report_list;
> >         struct list_head *report_ptr = report_list;
> > -       struct input_dev *dev = hidinput->input;
> > +       struct input_dev *dev;
> >         int error;
> >
> > +       if (list_empty(&hid->inputs)) {
> > +               hid_err(hid, "no inputs found\n");
> > +               return -ENODEV;
> > +       }
> > +       hidinput = list_entry(hid->inputs.next, struct hid_input, list);
> > +       dev = hidinput->input;
> > +
> >         if (list_empty(report_list)) {
> >                 hid_err(hid, "no output reports found\n");
> >                 return -ENODEV;