Null pointer dereference in cros-ec-typec

[Alyssa Ross]

My distribution recently enabled the Chrome OS EC Type C control driver
in its kernel builds.  On my Google Pixelbook i7 (eve), the driver reports
a null pointer dereference at boot.  From what I can tell, this happens
because typec->ec is set to NULL in cros_typec_probe.  Other drivers,
like cros-usbpd-notify, appear to be set up to handle this case.  As a
result of this bug, I'm no longer able to reboot my computer, because
udevd hangs while trying to do something with the device whose driver
isn't working.

Here's the full Oops.  I was able to reproduce the issue with every
kernel I tried, from 5.10 to mainline.

cros-usbpd-notify-acpi GOOG0003:00: Couldn't get Chrome EC device pointer.
input: Intel Virtual Buttons as /devices/pci0000:00/0000:00:1f.0/PNP0C09:00/INT33D6:00/input/input14
BUG: kernel NULL pointer dereference, address: 00000000000000d8
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
CPU: 1 PID: 561 Comm: systemd-udevd Not tainted 5.15.12 #4
Hardware name: Google Eve/Eve, BIOS MrChromebox-4.14 08/06/2021
RIP: 0010:__mutex_lock+0x59/0x8c0
Code: 53 48 89 cb 48 83 ec 70 89 75 9c be 3d 02 00 00 4c 89 45 90 e8 18 47 33 ff e8 e3 e2 ff ff 44 8b 35 a4 85 e8 02 45 85 f6 75 0a <4d> 3b 6d 68 0f 85 bf 07 00 00 65 ff 05 b6 5b 23 75 ff 75 90 4d 8d
RSP: 0018:ffffb44580a4bb50 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff8bf91320 RDI: ffff922cbba50e20
RBP: ffffb44580a4bbf0 R08: 0000000000000000 R09: ffff922c5bac8140
R10: ffffb44580a4bc10 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000070 R14: 0000000000000000 R15: 0000000000000001
FS:  00007f55338d6b40(0000) GS:ffff922fae200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000000d8 CR3: 000000011bbb2006 CR4: 00000000003706e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ? fs_reclaim_acquire+0x4d/0xd0
 ? lock_is_held_type+0xaa/0x120
 ? cros_ec_cmd_xfer_status+0x1f/0x110
 ? lock_is_held_type+0xaa/0x120
 ? cros_ec_cmd_xfer_status+0x1f/0x110
 cros_ec_cmd_xfer_status+0x1f/0x110
 cros_typec_ec_command+0x91/0x1c0 [cros_ec_typec]
 cros_typec_probe+0x7f/0x5a8 [cros_ec_typec]
 platform_probe+0x3f/0x90
 really_probe+0x1f5/0x3f0
 __driver_probe_device+0xfe/0x180
 driver_probe_device+0x1e/0x90
 __driver_attach+0xc4/0x1d0
 ? __device_attach_driver+0xe0/0xe0
 ? __device_attach_driver+0xe0/0xe0
 bus_for_each_dev+0x67/0x90
 bus_add_driver+0x12e/0x1f0
 driver_register+0x8f/0xe0
 ? 0xffffffffc04ec000
 do_one_initcall+0x67/0x320
 ? rcu_read_lock_sched_held+0x3f/0x80
 ? trace_kmalloc+0x38/0xe0
 ? kmem_cache_alloc_trace+0x17c/0x2b0
 do_init_module+0x5c/0x270
 __do_sys_finit_module+0x95/0xe0
 do_syscall_64+0x3b/0x90
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f55344b1f3d
Code: 5b 41 5c c3 66 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 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 73 01 c3 48 8b 0d bb ee 0e 00 f7 d8 64 89 01 48
RSP: 002b:00007fff187f1388 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
RAX: ffffffffffffffda RBX: 000055a53acbe6e0 RCX: 00007f55344b1f3d
RDX: 0000000000000000 RSI: 00007f553461732c RDI: 000000000000000e
RBP: 0000000000020000 R08: 0000000000000000 R09: 0000000000000002
R10: 000000000000000e R11: 0000000000000246 R12: 00007f553461732c
R13: 000055a53ad94010 R14: 0000000000000007 R15: 000055a53ad95690
 </TASK>
Modules linked in: fjes(+) cros_ec_typec(+) typec intel_vbtn(+) cros_usbpd_notify sparse_keymap soc_button_array int3403_thermal int340x_thermal_zone int3400_thermal acpi_thermal_rel cros_kbd_led_backlight zram ip_tables i915 hid_multitouch i2c_algo_bit ttm crct10dif_pclmul crc32_pclmul crc32c_intel drm_kms_helper nvme ghash_clmulni_intel sdhci_pci cqhci cec nvme_core sdhci serio_raw drm mmc_core i2c_hid_acpi i2c_hid video pinctrl_sunrisepoint fuse
CR2: 00000000000000d8
---[ end trace 4a12c4896d70352b ]---

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