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

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    e17994d1 usb: core: kcov: collect coverage from usb comple..
git tree:       https://github.com/google/kasan.git usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=13706939e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5d64370c438bc60
dashboard link: https://syzkaller.appspot.com/bug?extid=37ba33391ad5f3935bbd
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=150d3841e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12842b19e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+37ba33391ad5f3935bbd@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: slab-out-of-bounds in edge_interrupt_callback+0x8be/0x9d0 drivers/usb/serial/io_edgeport.c:715
Read of size 1 at addr ffff8881d2920c67 by task swapper/0/0

CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.6.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0xef/0x16e lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd3/0x314 mm/kasan/report.c:374
 __kasan_report.cold+0x37/0x77 mm/kasan/report.c:506
 kasan_report+0xe/0x20 mm/kasan/common.c:641
 edge_interrupt_callback+0x8be/0x9d0 drivers/usb/serial/io_edgeport.c:715
 __usb_hcd_giveback_urb+0x29a/0x550 drivers/usb/core/hcd.c:1650
 usb_hcd_giveback_urb+0x368/0x420 drivers/usb/core/hcd.c:1716
 dummy_timer+0x1258/0x32ae drivers/usb/gadget/udc/dummy_hcd.c:1966
 call_timer_fn+0x195/0x6f0 kernel/time/timer.c:1404


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