usb/misc/usbtest: null-ptr-deref in usbtest_probe/get_endpoints

[Andrey Konovalov]

Hi!

I've got the following report while fuzzing the kernel with syzkaller.

On commit dc972a67cc54585bd83ad811c4e9b6ab3dcd427e (4.14-rc2+).

It seems that out pointer ends up being NULL and kernel crashes on
access to out->desc.bEndpointAddress.

gadgetfs: bound to dummy_udc driver
usb 1-1: new full-speed USB device number 2 using dummy_hcd
gadgetfs: connected
gadgetfs: disconnected
gadgetfs: connected
usb 1-1: config 2 interface 0 altsetting 206 endpoint 0x81 has invalid
maxpacket 2040, setting to 64
usb 1-1: config 2 interface 0 altsetting 206 has an invalid endpoint
with address 0xFF, skipping
usb 1-1: config 2 interface 0 altsetting 206 endpoint 0x5 has an
invalid bInterval 255, changing to 4
usb 1-1: config 2 interface 0 has no altsetting 0
usb 1-1: New USB device found, idVendor=0525, idProduct=a4a0
usb 1-1: New USB device strings: Mfr=0, Product=185, SerialNumber=1
usb 1-1: Product: a
usb 1-1: SerialNumber: a
gadgetfs: configuration #2
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 1 PID: 1845 Comm: kworker/1:2 Not tainted
4.14.0-rc2-42664-gaf7d1481b3cb #297
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Workqueue: usb_hub_wq hub_event
task: ffff880064328000 task.stack: ffff880064398000
RIP: 0010:get_endpoints drivers/usb/misc/usbtest.c:208
RIP: 0010:usbtest_probe+0x114f/0x1ef0 drivers/usb/misc/usbtest.c:2706
RSP: 0018:ffff88006439e358 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 1ffff1000c873c33
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000002
RBP: ffff88006439e5e8 R08: ffff88006439dd60 R09: 1ffff1000c873bc5
R10: ffff880064328000 R11: 0000000000000005 R12: ffff88006197e698
R13: ffff880067755d28 R14: ffff88006439e5c0 R15: ffff88006782ddc0
FS: 0000000000000000(0000) GS:ffff88006c900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020002e07 CR3: 00000000639a9000 CR4: 00000000000006e0
Call Trace:
usb_probe_interface+0x35d/0x8e0 drivers/usb/core/driver.c:361
really_probe drivers/base/dd.c:413
driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
__device_attach_driver+0x230/0x290 drivers/base/dd.c:653
bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
__device_attach+0x26e/0x3d0 drivers/base/dd.c:710
device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
device_add+0xd0b/0x1660 drivers/base/core.c:1835
usb_set_configuration+0x104e/0x1870 drivers/usb/core/message.c:1932
generic_probe+0x73/0xe0 drivers/usb/core/generic.c:174
usb_probe_device+0xaf/0xe0 drivers/usb/core/driver.c:266
really_probe drivers/base/dd.c:413
driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
__device_attach_driver+0x230/0x290 drivers/base/dd.c:653
bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
__device_attach+0x26e/0x3d0 drivers/base/dd.c:710
device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
device_add+0xd0b/0x1660 drivers/base/core.c:1835
usb_new_device+0x7b8/0x1020 drivers/usb/core/hub.c:2457
hub_port_connect drivers/usb/core/hub.c:4903
hub_port_connect_change drivers/usb/core/hub.c:5009
port_event drivers/usb/core/hub.c:5115
hub_event+0x194d/0x3740 drivers/usb/core/hub.c:5195
process_one_work+0xc7f/0x1db0 kernel/workqueue.c:2119
worker_thread+0x221/0x1850 kernel/workqueue.c:2253
kthread+0x3a1/0x470 kernel/kthread.c:231
ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431
Code: 8b bd 30 fe ff ff e8 d1 60 05 fe 48 b8 00 00 00 00 00 fc ff df
41 89 5f 10 49 8b 9e c0 fe ff ff 48 8d 7b 02 48 89 fa 48 c1 ea 03 <0f>
b6 04 02 48 89 fa 83 e2 07 38 d0 7f 09 84 c0 74 05 e8 ba 5f
RIP: usbtest_probe+0x114f/0x1ef0 RSP: ffff88006439e358
---[ end trace 005817b8c41d50d0 ]---

[Alan Stern]

This looks like a simple logic error.

Alan Stern



Index: usb-4.x/drivers/usb/misc/usbtest.c
===================================================================
--- usb-4.x.orig/drivers/usb/misc/usbtest.c
+++ usb-4.x/drivers/usb/misc/usbtest.c
@@ -202,12 +202,13 @@ found:
return tmp;
}

- if (in) {
+ if (in)
dev->in_pipe = usb_rcvbulkpipe(udev,
in->desc.bEndpointAddress & USB_ENDPOINT_NUMBER_MASK);
+ if (out)
dev->out_pipe = usb_sndbulkpipe(udev,
out->desc.bEndpointAddress & USB_ENDPOINT_NUMBER_MASK);
- }
+
if (iso_in) {
dev->iso_in = &iso_in->desc;
dev->in_iso_pipe = usb_rcvisocpipe(udev,

[Andrey Konovalov]

Hi Alan,

This fixes it.

Tested-by: Andrey Konovalov <andre...@google.com>

Thanks!