KASAN: null-ptr-deref Write in submit_audio_out_urb

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    69bbe8c7 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=118b0aa2a00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c309d28e15db39c5
dashboard link: https://syzkaller.appspot.com/bug?extid=5255458d5e0a2b10bbb9
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11f4064ca00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14d51982a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+5255458d5e0a2b10bbb9@xxxxxxxxxxxxxxxxxxxxxxxxx

snd_usb_toneport 1-1:0.0: read request failed (error -110)
snd_usb_toneport 1-1:0.0: read request failed (error -110)
snd_usb_toneport 1-1:0.0: write request failed (error -110)
usb 1-1: send failed (error -110)
usb 1-1: send failed (error -110)
snd_usb_toneport 1-1:0.0: Line 6 POD Studio UX2 now attached
==================================================================
BUG: KASAN: null-ptr-deref in memset include/linux/string.h:344 [inline]
BUG: KASAN: null-ptr-deref in submit_audio_out_urb+0x919/0x1780  
sound/usb/line6/playback.c:246
Write of size 20 at addr 0000000000000010 by task kworker/1:2/2466

CPU: 1 PID: 2466 Comm: kworker/1:2 Not tainted 5.2.0-rc1+ #9
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events toneport_start_pcm
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0xca/0x13e lib/dump_stack.c:113
 __kasan_report.cold+0x5/0x32 mm/kasan/report.c:321
 kasan_report+0xe/0x20 mm/kasan/common.c:614
 memset+0x20/0x40 mm/kasan/common.c:107
 memset include/linux/string.h:344 [inline]
 submit_audio_out_urb+0x919/0x1780 sound/usb/line6/playback.c:246
 line6_submit_audio_out_all_urbs+0xc9/0x120 sound/usb/line6/playback.c:295
 line6_stream_start+0x156/0x1f0 sound/usb/line6/pcm.c:199
 line6_pcm_acquire+0x134/0x210 sound/usb/line6/pcm.c:322
 process_one_work+0x90a/0x1580 kernel/workqueue.c:2268
 worker_thread+0x96/0xe20 kernel/workqueue.c:2414
 kthread+0x30e/0x420 kernel/kthread.c:254
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
==================================================================
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 2466 Comm: kworker/1:2 Tainted: G    B             5.2.0-rc1+ #9
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events toneport_start_pcm
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0xca/0x13e lib/dump_stack.c:113
 panic+0x292/0x6df kernel/panic.c:218
 end_report+0x43/0x49 mm/kasan/report.c:95
 __kasan_report.cold+0xd/0x32 mm/kasan/report.c:324
 kasan_report+0xe/0x20 mm/kasan/common.c:614
 memset+0x20/0x40 mm/kasan/common.c:107
 memset include/linux/string.h:344 [inline]
 submit_audio_out_urb+0x919/0x1780 sound/usb/line6/playback.c:246
 line6_submit_audio_out_all_urbs+0xc9/0x120 sound/usb/line6/playback.c:295
 line6_stream_start+0x156/0x1f0 sound/usb/line6/pcm.c:199
 line6_pcm_acquire+0x134/0x210 sound/usb/line6/pcm.c:322
 process_one_work+0x90a/0x1580 kernel/workqueue.c:2268
 worker_thread+0x96/0xe20 kernel/workqueue.c:2414
 kthread+0x30e/0x420 kernel/kthread.c:254
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Kernel Offset: disabled
Rebooting in 86400 seconds..


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