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Message-ID: <20250424084429.3220757-1-akuchynski@chromium.org>
Date: Thu, 24 Apr 2025 08:44:27 +0000
From: Andrei Kuchynski <akuchynski@...omium.org>
To: Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jameson Thies <jthies@...gle.com>,
Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
Benson Leung <bleung@...omium.org>,
Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
Diogo Ivo <diogo.ivo@...nico.ulisboa.pt>,
Pooja Katiyar <pooja.katiyar@...el.com>,
Madhu M <madhu.m@...el.com>
Cc: linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org,
Andrei Kuchynski <akuchynski@...omium.org>
Subject: [PATCH v2 0/2] Fix thread synchronization issues
v2: ucsi_con_mutex_lock / ucsi_con_mutex_unlock functions are not longer
exported. Thanks to Heikki Krogerus for noticing it.
This patch series addresses deadlock issue and prevents a NULL pointer
access within the UCSI driver.
The first patch resolves a deadlock that occurs during partner device
removal. The deadlock scenario involves:
Thread 1: ucsi_handle_connector_change holding the connector mutex
(con->mutex) while waiting for dp_altmode_work() to complete
Thread 2: dp_altmode_work concurrently attempting to acquire the same mutex
Thread 3: ucsi_poll_worker is indirectly affected as it would be blocked
by the held mutex
The crash log:
INFO: task kworker/u16:16:7254 blocked for more than 122 seconds.
Not tainted 6.6.75-g5e7fdbab3246 #1
task:kworker/u16:16 state:D stack:0 pid:7254 ppid:2 flags:0x00000208
Workqueue: 16130000.spi:ec@0:typec ucsi_poll_worker [typec_ucsi]
Call trace:
__switch_to+0x130/0x158
__schedule+0x950/0xa18
schedule+0x68/0xc8
schedule_preempt_disabled+0x28/0x40
__mutex_lock+0x390/0xac0
__mutex_lock_slowpath+0x18/0x28
mutex_lock+0x28/0x60
ucsi_poll_worker+0x24/0x138 [typec_ucsi (HASH:5d4a 1)]
process_scheduled_works+0x258/0x4d8
worker_thread+0x330/0x428
kthread+0x108/0x1d0
ret_from_fork+0x10/0x20
INFO: task kworker/2:0:25045 blocked for more than 122 seconds.
Not tainted 6.6.75-g5e7fdbab3246 #1
task:kworker/2:0 state:D stack:0 pid:25045 ppid:2 flags:0x00000208
Workqueue: events dp_altmode_work [typec_displayport]
Call trace:
__switch_to+0x130/0x158
__schedule+0x950/0xa18
schedule+0x68/0xc8
schedule_preempt_disabled+0x28/0x40
__mutex_lock+0x390/0xac0
__mutex_lock_slowpath+0x18/0x28
mutex_lock+0x28/0x60
ucsi_displayport_enter+0x44/0x160 [typec_ucsi (HASH:5d4a 1)]
typec_altmode_enter+0x110/0x120
dp_altmode_work+0xe8/0x170 [typec_displayport (HASH:c690 2)]
process_scheduled_works+0x258/0x4d8
worker_thread+0x330/0x428
kthread+0x108/0x1d0
ret_from_fork+0x10/0x20
INFO: task kworker/2:3:25952 blocked for more than 122 seconds.
Not tainted 6.6.75-g5e7fdbab3246 #1
task:kworker/2:3 state:D stack:0 pid:25952 ppid:2 flags:0x00000208
Workqueue: events ucsi_handle_connector_change [typec_ucsi]
Call trace:
__switch_to+0x130/0x158
__schedule+0x950/0xa18
schedule+0x68/0xc8
schedule_timeout+0x44/0x1b8
wait_for_common+0xe4/0x1d8
wait_for_completion+0x1c/0x30
__flush_work+0x22c/0x2a8
__cancel_work_timer+0x130/0x1d8
cancel_work_sync+0x18/0x30
dp_altmode_remove+0x20/0x70 [typec_displayport (HASH:c690 2)]
typec_remove+0x60/0x120
device_release_driver_internal+0x164/0x258
device_release_driver+0x1c/0x30
bus_remove_device+0x140/0x160
device_del+0x1c0/0x330
device_unregister+0x1c/0x40
typec_unregister_altmode+0x40/0x58
ucsi_unregister_partner+0x90/0x170 [typec_ucsi (HASH:5d4a 1)]
ucsi_handle_connector_change+0x184/0x468 [typec_ucsi (HASH:5d4a 1)]
process_scheduled_works+0x258/0x4d8
worker_thread+0x330/0x428
kthread+0x108/0x1d0
ret_from_fork+0x10/0x20
The second patch prevents a NULL pointer access that occurs if
ucsi_displayport_work is still accessing partner-related data after
the partner has been unregistered.
The crash log:
BUG: kernel NULL pointer dereference, address: 0000000000000300
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 3 PID: 3413 Comm: kworker/3:3 Tainted: G U 6.6.76-07480
Hardware name: Google Brox/Brox, BIOS Google_Brox.16080.59.0 12/18/2024
Workqueue: events ucsi_displayport_work [typec_ucsi]
RIP: 0010:typec_altmode_vdm+0x8f/0x4d0 [typec]
RSP: 0018:ffffa929c825fe28 EFLAGS: 00010246
RAX: 0000000000000014 RBX: 0000000000000001 RCX: 43032ac4505ac800
RDX: ffff9d8def8e77c0 RSI: ffff9d8def8db5c8 RDI: ffff9d8def8db5c8
RBP: ffffa929c825fe50 R08: 0000000000001fff R09: ffffffff9385e1e0
R10: 0000000000005ffd R11: 00000000ffffdfff R12: ffff9d8ab4b67c08
R13: 0000000000000000 R14: 0000000000000000 R15: 00000000ff01a144
FS: 0000000000000000(0000) GS:ffff9d8def8c0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000300 CR3: 0000000148438000 CR4: 0000000000750ee0
PKRU: 55555554
Call Trace:
? __die_body+0xae/0xb0
? page_fault_oops+0x381/0x3e0
? prb_read_valid+0x29/0x50
? exc_page_fault+0x4f/0xa0
? asm_exc_page_fault+0x22/0x30
? typec_altmode_vdm+0x8f/0x4d0 [typec (HASH:c6ec 5)]
? typec_altmode_vdm+0x87/0x4d0 [typec (HASH:c6ec 5)]
ucsi_displayport_work+0x34/0x70 [typec_ucsi (HASH:698a 6)]
worker_thread+0x386/0x930
Andrei Kuchynski (2):
usb: typec: ucsi: displayport: Fix deadlock
usb: typec: ucsi: displayport: Fix NULL pointer access
drivers/usb/typec/ucsi/displayport.c | 21 ++++++++++-------
drivers/usb/typec/ucsi/ucsi.c | 34 ++++++++++++++++++++++++++++
drivers/usb/typec/ucsi/ucsi.h | 2 ++
3 files changed, 49 insertions(+), 8 deletions(-)
--
2.49.0.805.g082f7c87e0-goog
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