[PATCH 5.4 23/54] thunderbolt: Fix use-after-free in remove_unplugged_switch()

Greg Kroah-Hartman
2020-12-10T14:44:02Z

From: Mika Westerberg <mika.westerberg@linux.intel.com>

commit 600c0849cf86b75d86352f59745226273290986a upstream.

Paulian reported a crash that happens when a dock is unplugged during
hibernation:

[78436.228217] thunderbolt 0-1: device disconnected
[78436.228365] BUG: kernel NULL pointer dereference, address: 00000000000001e0
...
[78436.228397] RIP: 0010:icm_free_unplugged_children+0x109/0x1a0
...
[78436.228432] Call Trace:
[78436.228439] icm_rescan_work+0x24/0x30
[78436.228444] process_one_work+0x1a3/0x3a0
[78436.228449] worker_thread+0x30/0x370
[78436.228454] ? process_one_work+0x3a0/0x3a0
[78436.228457] kthread+0x13d/0x160
[78436.228461] ? kthread_park+0x90/0x90
[78436.228465] ret_from_fork+0x1f/0x30

This happens because remove_unplugged_switch() calls tb_switch_remove()
that releases the memory pointed by sw so the following lines reference
to a memory that might be released already.

Fix this by saving pointer to the parent device before calling
tb_switch_remove().

Reported-by: Paulian Bogdan Marinca <paulian@marinca.net>
Fixes: 4f7c2e0d8765 ("thunderbolt: Make sure device runtime resume completes before taking domain lock")
Cc: stable@vger.kernel.org
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/thunderbolt/icm.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

--- a/drivers/thunderbolt/icm.c
+++ b/drivers/thunderbolt/icm.c
@@ -1919,7 +1919,9 @@ static int complete_rpm(struct device *d

static void remove_unplugged_switch(struct tb_switch *sw)
{
- pm_runtime_get_sync(sw->dev.parent);
+ struct device *parent = get_device(sw->dev.parent);
+
+ pm_runtime_get_sync(parent);

/*
* Signal this and switches below for rpm_complete because
@@ -1930,8 +1932,10 @@ static void remove_unplugged_switch(stru
bus_for_each_dev(&tb_bus_type, &sw->dev, NULL, complete_rpm);
tb_switch_remove(sw);

- pm_runtime_mark_last_busy(sw->dev.parent);
- pm_runtime_put_autosuspend(sw->dev.parent);
+ pm_runtime_mark_last_busy(parent);
+ pm_runtime_put_autosuspend(parent);
+
+ put_device(parent);
}

static void icm_free_unplugged_children(struct tb_switch *sw)