[PATCH] thunderbolt: Fix use-after-free in remove_unplugged_switch()

[PATCH] thunderbolt: Fix use-after-free in remove_unplugged_switch()

[Mika Westerberg]

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>
---
 drivers/thunderbolt/icm.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/thunderbolt/icm.c b/drivers/thunderbolt/icm.c
index b51fc3f62b1f..05323c442b56 100644
--- a/drivers/thunderbolt/icm.c
+++ b/drivers/thunderbolt/icm.c
@@ -1976,7 +1976,9 @@ static int complete_rpm(struct device *dev, void *data)
 
 static void remove_unplugged_switch(struct tb_switch *sw)
 {
-	pm_runtime_get_sync(sw->dev.parent);
+	struct device *parent = sw->dev.parent;
+
+	pm_runtime_get_sync(parent);
 
 	/*
 	 * Signal this and switches below for rpm_complete because
@@ -1987,8 +1989,8 @@ static void remove_unplugged_switch(struct tb_switch *sw)
 	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);
 }
 
 static void icm_free_unplugged_children(struct tb_switch *sw)
-- 
2.29.2

Re: [PATCH] thunderbolt: Fix use-after-free in remove_unplugged_switch()

[Greg KH]

On Wed, Nov 18, 2020 at 04:37:45PM +0300, Mika Westerberg wrote:
> 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>
> ---
>  drivers/thunderbolt/icm.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/thunderbolt/icm.c b/drivers/thunderbolt/icm.c
> index b51fc3f62b1f..05323c442b56 100644
> --- a/drivers/thunderbolt/icm.c
> +++ b/drivers/thunderbolt/icm.c
> @@ -1976,7 +1976,9 @@ static int complete_rpm(struct device *dev, void *data)
>  
>  static void remove_unplugged_switch(struct tb_switch *sw)
>  {
> -	pm_runtime_get_sync(sw->dev.parent);
> +	struct device *parent = sw->dev.parent;
> +
> +	pm_runtime_get_sync(parent);

If you are saving a pointer to a structure, shouldn't you increment the
reference count?

	struct device *parent = get_device(sw->dev.parent);

Then you know it is valid when you use it later on.

Just remember to call put_device() when you are done.

thanks,

greg k-h

Re: [PATCH] thunderbolt: Fix use-after-free in remove_unplugged_switch()

[Mika Westerberg]

On Wed, Nov 18, 2020 at 02:47:27PM +0100, Greg KH wrote:
> On Wed, Nov 18, 2020 at 04:37:45PM +0300, Mika Westerberg wrote:
> > 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>
> > ---
> >  drivers/thunderbolt/icm.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/thunderbolt/icm.c b/drivers/thunderbolt/icm.c
> > index b51fc3f62b1f..05323c442b56 100644
> > --- a/drivers/thunderbolt/icm.c
> > +++ b/drivers/thunderbolt/icm.c
> > @@ -1976,7 +1976,9 @@ static int complete_rpm(struct device *dev, void *data)
> >  
> >  static void remove_unplugged_switch(struct tb_switch *sw)
> >  {
> > -	pm_runtime_get_sync(sw->dev.parent);
> > +	struct device *parent = sw->dev.parent;
> > +
> > +	pm_runtime_get_sync(parent);
> 
> If you are saving a pointer to a structure, shouldn't you increment the
> reference count?
> 
> 	struct device *parent = get_device(sw->dev.parent);
> 
> Then you know it is valid when you use it later on.

Indeed, I missed that.

> Just remember to call put_device() when you are done.

Sure I'll do this in v2. Thanks!