KASAN: slab-out-of-bounds Write in snd_usb_mixer_notify_id

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 7ae77150 Merge tag 'powerpc-5.8-1' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14a0b46e100000
kernel config: https://syzkaller.appspot.com/x/.config?x=d195fe572fb15312
dashboard link: https://syzkaller.appspot.com/bug?extid=fb14314433463ad51625
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11bb9d35100000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1309c569100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+fb1431...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in snd_usb_mixer_notify_id+0x219/0x2a0 sound/usb/mixer.c:3240
Write of size 4 at addr ffff888095d78ce0 by task swapper/1/0

CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.7.0-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+0x188/0x20d lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xd3/0x413 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
snd_usb_mixer_notify_id+0x219/0x2a0 sound/usb/mixer.c:3240
snd_usb_mixer_interrupt+0x416/0x980 sound/usb/mixer.c:3379
__usb_hcd_giveback_urb+0x2af/0x4b0 drivers/usb/core/hcd.c:1650
usb_hcd_giveback_urb+0x368/0x420 drivers/usb/core/hcd.c:1716
__skb_queue_head_init include/linux/skbuff.h:1854 [inline]
skbpoolfree drivers/block/aoe/aoedev.c:435 [inline]
freedev drivers/block/aoe/aoedev.c:290 [inline]
dummy_timer+0x1243/0x2fe1 drivers/block/aoe/aoedev.c:366
call_timer_fn+0x1ac/0x780 kernel/time/timer.c:1404
expire_timers kernel/time/timer.c:1449 [inline]
__run_timers kernel/time/timer.c:1773 [inline]
__run_timers kernel/time/timer.c:1740 [inline]
run_timer_softirq+0x623/0x1600 kernel/time/timer.c:1786


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