divide error in usbtmc_generic_read

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: d0847550 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=16295d4a600000
kernel config: https://syzkaller.appspot.com/x/.config?x=dbc9c80cc095da19
dashboard link: https://syzkaller.appspot.com/bug?extid=55b0304b360654a7537b
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1288a31c600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15282e86600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+55b030...@syzkaller.appspotmail.com

divide error: 0000 [#1] SMP KASAN
CPU: 1 PID: 1761 Comm: syz-executor063 Not tainted 5.3.0-rc4+ #26
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:usbtmc_generic_read+0x135/0x1190 drivers/usb/class/usbtmc.c:816
Code: 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 01 38 d0 7c 08 84 d2
0f 85 50 08 00 00 41 0f b7 6e 34 31 d2 31 ff 8b 44 24 28 <f7> f5 89 d6 41
89 d4 e8 2f 54 c9 fd 44 8b 6c 24 28 45 85 e4 44 89
RSP: 0018:ffff8881d2b77a58 EFLAGS: 00010246
RAX: 0000000000000002 RBX: 000000004f894bad RCX: ffffffff837487cd
RDX: 0000000000000000 RSI: ffffffff837487da RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff8881d20a0000 R09: ffffed103a56ef90
R10: ffffed103a56ef8f R11: 0000000000000003 R12: ffff8881d08e7180
R13: 0000000020000000 R14: ffff8881d0404c80 R15: ffff8881d08e7180
FS: 0000555555b74880(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006cc090 CR3: 00000001d615e000 CR4: 00000000001406e0
Call Trace:
usbtmc_ioctl_generic_read drivers/usb/class/usbtmc.c:1029 [inline]
usbtmc_ioctl+0x27d/0x2ab0 drivers/usb/class/usbtmc.c:2089
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:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4419a9
Code: e8 8c e8 ff ff 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 cb 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffd0abd6738 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004419a9
RDX: 0000000020000000 RSI: 00000000c0145b0e RDI: 0000000000000004
RBP: 000000000000a984 R08: 000000000000000f R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402700
R13: 0000000000402790 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace a91d281a4d83213c ]---
RIP: 0010:usbtmc_generic_read+0x135/0x1190 drivers/usb/class/usbtmc.c:816
Code: 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 01 38 d0 7c 08 84 d2
0f 85 50 08 00 00 41 0f b7 6e 34 31 d2 31 ff 8b 44 24 28 <f7> f5 89 d6 41
89 d4 e8 2f 54 c9 fd 44 8b 6c 24 28 45 85 e4 44 89
RSP: 0018:ffff8881d2b77a58 EFLAGS: 00010246
RAX: 0000000000000002 RBX: 000000004f894bad RCX: ffffffff837487cd
RDX: 0000000000000000 RSI: ffffffff837487da RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff8881d20a0000 R09: ffffed103a56ef90
R10: ffffed103a56ef8f R11: 0000000000000003 R12: ffff8881d08e7180
R13: 0000000020000000 R14: ffff8881d0404c80 R15: ffff8881d08e7180
FS: 0000555555b74880(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006cc090 CR3: 00000001d615e000 CR4: 00000000001406e0


---
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 syzk...@googlegroups.com.

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

[Oliver Neukum]

Am Mittwoch, den 14.08.2019, 04:38 -0700 schrieb syzbot:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: d0847550 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=16295d4a600000
> kernel config: https://syzkaller.appspot.com/x/.config?x=dbc9c80cc095da19
> dashboard link: https://syzkaller.appspot.com/bug?extid=55b0304b360654a7537b
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1288a31c600000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15282e86600000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+55b030...@syzkaller.appspotmail.com

#syz test: https://github.com/google/kasan.git d0847550

From 5fa900e86e57d92a0b23a1a60ff4f4f13e997a93 Mon Sep 17 00:00:00 2001
From: Oliver Neukum <one...@suse.com>
Date: Wed, 14 Aug 2019 15:21:41 +0200
Subject: [PATCH] usbtmc: more sanity checking for packet size

A malicious device can make the driver divide ny zero
with a nonsense maximum packet size.

SIgned-off-by: Oliver Neukum <one...@suse.com>
---
drivers/usb/class/usbtmc.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index 4942122b2346..11042ca56818 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -2364,6 +2364,8 @@ static int usbtmc_probe(struct usb_interface *intf,

data->bulk_in = bulk_in->bEndpointAddress;
data->wMaxPacketSize = usb_endpoint_maxp(bulk_in);
+ if (!data->wMaxPacketSize)
+ goto err_put;
dev_dbg(&intf->dev, "Found bulk in endpoint at %u\n", data->bulk_in);

data->bulk_out = bulk_out->bEndpointAddress;
--
2.16.4

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer still triggered
crash:
KASAN: use-after-free Read in usbtmc_disconnect

usb 5-1: USB disconnect, device number 2
==================================================================
BUG: KASAN: use-after-free in __mutex_lock_common
kernel/locking/mutex.c:912 [inline]
BUG: KASAN: use-after-free in __mutex_lock+0xf23/0x1360
kernel/locking/mutex.c:1077
Read of size 8 at addr ffff8881d63299c8 by task kworker/1:0/17

CPU: 1 PID: 17 Comm: kworker/1:0 Not tainted 5.3.0-rc4+ #1

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:612
__mutex_lock_common kernel/locking/mutex.c:912 [inline]
__mutex_lock+0xf23/0x1360 kernel/locking/mutex.c:1077
usbtmc_disconnect+0x58/0x180 drivers/usb/class/usbtmc.c:2443
usb_unbind_interface+0x1bd/0x8a0 drivers/usb/core/driver.c:423
__device_release_driver drivers/base/dd.c:1134 [inline]
device_release_driver_internal+0x42f/0x500 drivers/base/dd.c:1165
bus_remove_device+0x2dc/0x4a0 drivers/base/bus.c:556
device_del+0x420/0xb10 drivers/base/core.c:2339
usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237
usb_disconnect+0x284/0x8d0 drivers/usb/core/hub.c:2199
hub_port_connect drivers/usb/core/hub.c:4949 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
port_event drivers/usb/core/hub.c:5359 [inline]
hub_event+0x1454/0x3640 drivers/usb/core/hub.c:5441
process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
worker_thread+0x96/0xe20 kernel/workqueue.c:2415
kthread+0x318/0x420 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Allocated by task 1737:
save_stack+0x1b/0x80 mm/kasan/common.c:69
set_track mm/kasan/common.c:77 [inline]
__kasan_kmalloc mm/kasan/common.c:487 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:460
kmalloc include/linux/slab.h:552 [inline]
kzalloc include/linux/slab.h:748 [inline]
usbtmc_probe+0xad/0x1360 drivers/usb/class/usbtmc.c:2328
usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
really_probe+0x281/0x6d0 drivers/base/dd.c:548
driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
__device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:454
__device_attach+0x217/0x360 drivers/base/dd.c:894
bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
device_add+0xae6/0x16f0 drivers/base/core.c:2165
usb_set_configuration+0xdf6/0x1670 drivers/usb/core/message.c:2023
generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
really_probe+0x281/0x6d0 drivers/base/dd.c:548
driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
__device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:454
__device_attach+0x217/0x360 drivers/base/dd.c:894
bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
device_add+0xae6/0x16f0 drivers/base/core.c:2165
usb_new_device.cold+0x6a4/0xe79 drivers/usb/core/hub.c:2536
hub_port_connect drivers/usb/core/hub.c:5098 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
port_event drivers/usb/core/hub.c:5359 [inline]
hub_event+0x1b5c/0x3640 drivers/usb/core/hub.c:5441
process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
worker_thread+0x96/0xe20 kernel/workqueue.c:2415
kthread+0x318/0x420 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Freed by task 1737:
save_stack+0x1b/0x80 mm/kasan/common.c:69
set_track mm/kasan/common.c:77 [inline]
__kasan_slab_free+0x130/0x180 mm/kasan/common.c:449
slab_free_hook mm/slub.c:1423 [inline]
slab_free_freelist_hook mm/slub.c:1474 [inline]
slab_free mm/slub.c:3016 [inline]
kfree+0xe4/0x2f0 mm/slub.c:3957
kref_put include/linux/kref.h:65 [inline]
usbtmc_probe+0x55c/0x1360 drivers/usb/class/usbtmc.c:2433
usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
really_probe+0x281/0x6d0 drivers/base/dd.c:548
driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
__device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:454
__device_attach+0x217/0x360 drivers/base/dd.c:894
bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
device_add+0xae6/0x16f0 drivers/base/core.c:2165
usb_set_configuration+0xdf6/0x1670 drivers/usb/core/message.c:2023
generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
really_probe+0x281/0x6d0 drivers/base/dd.c:548
driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
__device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:454
__device_attach+0x217/0x360 drivers/base/dd.c:894
bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
device_add+0xae6/0x16f0 drivers/base/core.c:2165
usb_new_device.cold+0x6a4/0xe79 drivers/usb/core/hub.c:2536
hub_port_connect drivers/usb/core/hub.c:5098 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
port_event drivers/usb/core/hub.c:5359 [inline]
hub_event+0x1b5c/0x3640 drivers/usb/core/hub.c:5441
process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
worker_thread+0x96/0xe20 kernel/workqueue.c:2415
kthread+0x318/0x420 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff8881d6329900
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 200 bytes inside of
512-byte region [ffff8881d6329900, ffff8881d6329b00)
The buggy address belongs to the page:
page:ffffea000758ca00 refcount:1 mapcount:0 mapping:ffff8881da002500
index:0x0 compound_mapcount: 0
flags: 0x200000000010200(slab|head)
raw: 0200000000010200 ffffea0007585680 0000000700000007 ffff8881da002500
raw: 0000000000000000 00000000000c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881d6329880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881d6329900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8881d6329980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881d6329a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881d6329a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit: d0847550 usb-fuzzer: main usb gadget fuzzer driver
git tree: https://github.com/google/kasan.git

console output: https://syzkaller.appspot.com/x/log.txt?x=10ac29ee600000
kernel config: https://syzkaller.appspot.com/x/.config?x=dbc9c80cc095da19

compiler: gcc (GCC) 9.0.0 20181231 (experimental)

patch: https://syzkaller.appspot.com/x/patch.diff?x=11f3b2e2600000

[Andrey Konovalov]

On Wed, Aug 14, 2019 at 3:38 PM syzbot
<syzbot+55b030...@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot has tested the proposed patch but the reproducer still triggered
> crash:
> KASAN: use-after-free Read in usbtmc_disconnect

Looks like a different bug in the same driver that gets triggered by
the same reproducer =)

You fix looks good to me.

[Guido Kiener]

Hi Oliver,

Thanks for the fix. You need to set an invalid return code, too.

Regards,

Guido

[Oliver Neukum]

Am Mittwoch, den 14.08.2019, 06:38 -0700 schrieb syzbot:
> syzbot has tested the proposed patch but the reproducer still triggered
> crash:
> KASAN: use-after-free Read in usbtmc_disconnect

I am afraid that is a difficiency in KASAN that should be fixed.
Is the class of the error compared if I leave in more of the
original bug report? Actually the ID is still there, so it really
should return an inconclusive in these cases.

Regards
Oliver

[Oliver Neukum]

Am Mittwoch, den 14.08.2019, 04:38 -0700 schrieb syzbot:

> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: d0847550 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=16295d4a600000
> kernel config: https://syzkaller.appspot.com/x/.config?x=dbc9c80cc095da19
> dashboard link: https://syzkaller.appspot.com/bug?extid=55b0304b360654a7537b
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1288a31c600000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15282e86600000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+55b030...@syzkaller.appspotmail.com

#syz test: https://github.com/google/kasan.git d0847550

From df64f5cd2e6a9b43c75bb7e3276b8805a225db75 Mon Sep 17 00:00:00 2001

From: Oliver Neukum <one...@suse.com>
Date: Wed, 14 Aug 2019 15:21:41 +0200
Subject: [PATCH] usbtmc: more sanity checking for packet size

A malicious device can make the driver divide ny zero
with a nonsense maximum packet size.

V2: return a sensible error code

SIgned-off-by: Oliver Neukum <one...@suse.com>
---

drivers/usb/class/usbtmc.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index 4942122b2346..36858ddd8d9b 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -2362,8 +2362,11 @@ static int usbtmc_probe(struct usb_interface *intf,
goto err_put;
}

+ retcode = -EINVAL;

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger
crash:

Reported-and-tested-by:
syzbot+55b030...@syzkaller.appspotmail.com

Tested on:

commit: d0847550 usb-fuzzer: main usb gadget fuzzer driver
git tree: https://github.com/google/kasan.git

kernel config: https://syzkaller.appspot.com/x/.config?x=dbc9c80cc095da19

compiler: gcc (GCC) 9.0.0 20181231 (experimental)

patch: https://syzkaller.appspot.com/x/patch.diff?x=15e22d02600000

Note: testing is done by a robot and is best-effort only.

[Andrey Konovalov]

I don't get this, what kind of deficiency do you mean?

Anyway, looks like I was wrong, the reported use-after-free is caused
by an incomplete fix, and setting the right retcode fixes the
use-after-free.

[Oliver Neukum]

Am Montag, den 19.08.2019, 14:17 +0200 schrieb Andrey Konovalov:
> On Thu, Aug 15, 2019 at 3:31 PM Oliver Neukum <one...@suse.com> wrote:
> >
> > Am Mittwoch, den 14.08.2019, 06:38 -0700 schrieb syzbot:
> > > syzbot has tested the proposed patch but the reproducer still triggered
> > > crash:
> > > KASAN: use-after-free Read in usbtmc_disconnect
> >
> > I am afraid that is a difficiency in KASAN that should be fixed.
> > Is the class of the error compared if I leave in more of the
> > original bug report? Actually the ID is still there, so it really
> > should return an inconclusive in these cases.
>
> I don't get this, what kind of deficiency do you mean?

The original error was a divide by zero. The first fix fixed that
but still another error showed up. If I propose a fix there are
other possibilities besides it working.

I could have no effect on the original bug or my fix breaks
something else and KASAN is making no difference between
those cases.

Regards
Oliver

[Andrey Konovalov]

I think you mean syzbot here and not KASAN. Do I understand correctly,
that you're saying that the original report was divide-by-zero, but
when you requested to test the patch the reproducer triggered a
use-after-free, and syzbot didn't treat the patch you provided as a
correct fix? In this case this is working as intended, as a bug
(especially some race) can manifest in different ways, so the kernel
might crash with a different stack trace.

[Oliver Neukum]

Am Montag, den 19.08.2019, 14:43 +0200 schrieb Andrey Konovalov:
> On Mon, Aug 19, 2019 at 2:37 PM Oliver Neukum <one...@suse.com> wrote:

> > The original error was a divide by zero. The first fix fixed that
> > but still another error showed up. If I propose a fix there are
> > other possibilities besides it working.
> >
> > I could have no effect on the original bug or my fix breaks
> > something else and KASAN is making no difference between
> > those cases.
>
> I think you mean syzbot here and not KASAN. Do I understand correctly,
> that you're saying that the original report was

Yes, sorry syzbot.

> divide-by-zero, but
> when you requested to test the patch the reproducer triggered a
> use-after-free, and syzbot didn't treat the patch you provided as a
> correct fix?

No, obviously there is still a bug. What I would like syzbot to have
would be a third category: inconclusive.
Seeing another bug instead may also mean the first bug struck
before the second could ever happen. We just lack data to tell.

Regards
Oliver

[Andrey Konovalov]

OK, I see. The exact words that syzbot uses in this case are "syzbot

has tested the proposed patch but the reproducer still triggered

crash". What would you like to see instead?

[Oliver Neukum]

"syzbot has tested the proposed patch but the reproducer triggered
another crash" would make it clearer.

Regards
Oliver

[Andrey Konovalov]

This implies that we can differentiate between different crashes. We
can differentiate between different manifestations of crashes, but
those can be caused by the same bug. I think we can remove the word
"still" though, so the words will be: "syzbot has tested the proposed
patch, but the reproducer triggered a crash".

Dmitry, WDYT?

[Oliver Neukum]

Am Montag, den 19.08.2019, 17:40 +0200 schrieb Andrey Konovalov:
>
> This implies that we can differentiate between different crashes. We
> can differentiate between different manifestations of crashes, but
> those can be caused by the same bug. I think we can remove the word
> "still" though, so the words will be: "syzbot has tested the proposed
> patch, but the reproducer triggered a crash".

That is exactly my point. There are three cases:

- no crash
- clearly the same crash
- something

Yet syzbot has two answers only. We are killing information needlessly.

Regards
Oliver

[Andrey Konovalov]

#syz fix: usbtmc: more sanity checking for packet size