2023-10-04 15:26:57

by Javier Carrasco

Subject: [PATCH v3] Input: powermate - fix use-after-free in powermate_config_complete

syzbot has found a use-after-free bug [1] in the powermate driver. This
happens when the device is disconnected, which leads to a memory free
from the powermate_device struct.
When an asynchronous control message completes after the kfree and its
callback is invoked, the lock does not exist anymore and hence the bug.

Use usb_kill_urb() on pm->config to cancel any in-progress requests upon
device disconnection.

[1] https://syzkaller.appspot.com/bug?extid=0434ac83f907a1dbdd1e

Signed-off-by: Javier Carrasco <[email protected]>
Reported-by: [email protected]
---
Changes in v3:
- Let usb_kill_urb on pm->irq where it is i.e. before unregistering the
device.
- Link to v2: https://lore.kernel.org/r/20230916-topic-powermate_use_after_free-v2-1-505f49019f2f@gmail.com

Changes in v2:
- Use usb_kill_urb() on pm->config upon device disconnection.
- Link to v1: https://lore.kernel.org/r/20230916-topic-powermate_use_after_free-v1-1-2ffa46652869@gmail.com
---
drivers/input/misc/powermate.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/input/misc/powermate.c b/drivers/input/misc/powermate.c
index c1c733a9cb89..db2ba89adaef 100644
--- a/drivers/input/misc/powermate.c
+++ b/drivers/input/misc/powermate.c
@@ -425,6 +425,7 @@ static void powermate_disconnect(struct usb_interface *intf)
pm->requires_update = 0;
usb_kill_urb(pm->irq);
input_unregister_device(pm->input);
+ usb_kill_urb(pm->config);
usb_free_urb(pm->irq);
usb_free_urb(pm->config);
powermate_free_buffers(interface_to_usbdev(intf), pm);

---
base-commit: cefc06e4de1477dbdc3cb2a91d4b1873b7797a5c
change-id: 20230916-topic-powermate_use_after_free-c703c7969c91

Best regards,
--
Javier Carrasco <[email protected]>

2023-10-14 03:14:12

by Dmitry Torokhov

Subject: Re: [PATCH v3] Input: powermate - fix use-after-free in powermate_config_complete

On Wed, Oct 04, 2023 at 04:36:13PM +0200, Javier Carrasco wrote:
> syzbot has found a use-after-free bug [1] in the powermate driver. This
> happens when the device is disconnected, which leads to a memory free
> from the powermate_device struct.
> When an asynchronous control message completes after the kfree and its
> callback is invoked, the lock does not exist anymore and hence the bug.
>
> Use usb_kill_urb() on pm->config to cancel any in-progress requests upon
> device disconnection.
>
> [1] https://syzkaller.appspot.com/bug?extid=0434ac83f907a1dbdd1e
>
> Signed-off-by: Javier Carrasco <[email protected]>
> Reported-by: [email protected]

Applied, thank you.

--
Dmitry