KASAN: slab-out-of-bounds Read in hiddev_ioctl_usage

[syzbot <syzbot+a3f4c2f4f8cde2ff797b@syzkaller.appspotmail.com>]

Hello,

syzbot found the following crash on:

HEAD commit:    2994c077 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=15170f6d600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=69ddefac6929256a
dashboard link: https://syzkaller.appspot.com/bug?extid=a3f4c2f4f8cde2ff797b
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14a1a55b600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=107c47bd600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a3f4c2f4f8cde2ff797b@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in hiddev_ioctl_usage.isra.0+0x12d0/0x13b0  
drivers/hid/usbhid/hiddev.c:535
Read of size 4 at addr ffff8881d3fc81dc by task syz-executor894/1724

CPU: 0 PID: 1724 Comm: syz-executor894 Not tainted 5.3.0+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0xca/0x13e lib/dump_stack.c:113
  print_address_description.constprop.0+0x36/0x50 mm/kasan/report.c:374
  __kasan_report.cold+0x1a/0x33 mm/kasan/report.c:506
  kasan_report+0xe/0x12 mm/kasan/common.c:634
  hiddev_ioctl_usage.isra.0+0x12d0/0x13b0 drivers/hid/usbhid/hiddev.c:535
  hiddev_ioctl+0x7a1/0x1550 drivers/hid/usbhid/hiddev.c:807
  vfs_ioctl fs/ioctl.c:46 [inline]
  file_ioctl fs/ioctl.c:509 [inline]
  do_vfs_ioctl+0xd2d/0x1330 fs/ioctl.c:696
  ksys_ioctl+0x9b/0xc0 fs/ioctl.c:713
  __do_sys_ioctl fs/ioctl.c:720 [inline]
  __se_sys_ioctl fs/ioctl.c:718 [inline]
  __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:718
  do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x444969
Code: e8 bc af 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 1b d8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffff4d72ed8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004002e0 RCX: 0000000000444969
RDX: 0000000020000100 RSI: 00000000c018480b RDI: 0000000000000004
RBP: 00000000006cf018 R08: 8fce4d9635172f21 R09: 00000000004002e0
R10: 000000000000000f R11: 0000000000000246 R12: 0000000000402610
R13: 00000000004026a0 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea00074fe000 refcount:1 mapcount:0 mapping:0000000000000000  
index:0x0 compound_mapcount: 0
flags: 0x200000000010000(head)
raw: 0200000000010000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8881d3fc8080: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
  ffff8881d3fc8100: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
> ffff8881d3fc8180: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
                                                     ^
  ffff8881d3fc8200: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
  ffff8881d3fc8280: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
==================================================================


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