The original code puts flush_work() before timer_shutdown_sync()
in switch_drv_remove(). Although we use flush_work() to stop
the worker, it could be re-scheduled in switch_timer. As a result,
the UAF bug will happen. The detail is shown below:
(cpu 0) | (cpu 1)
switch_drv_remove() |
flush_work() |
... | switch_timer //timer
| schedule_work(&psw->work)
timer_shutdown_sync() |
... | switch_work_handler //worker
kfree(psw) //free |
| psw->state = 0 //use
This patch puts timer_shutdown_sync() before flush_work() to
mitigate the bugs. As a result, the worker and timer could
be stopped safely before the deallocate operations.
Fixes: 9f5e8eee5cfe ("sh: generic push-switch framework.")
Signed-off-by: Duoming Zhou <[email protected]>
---
arch/sh/drivers/push-switch.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/sh/drivers/push-switch.c b/arch/sh/drivers/push-switch.c
index c95f48ff3f6..6ecba5f521e 100644
--- a/arch/sh/drivers/push-switch.c
+++ b/arch/sh/drivers/push-switch.c
@@ -101,8 +101,8 @@ static int switch_drv_remove(struct platform_device *pdev)
device_remove_file(&pdev->dev, &dev_attr_switch);
platform_set_drvdata(pdev, NULL);
- flush_work(&psw->work);
timer_shutdown_sync(&psw->debounce);
+ flush_work(&psw->work);
free_irq(irq, pdev);
kfree(psw);
--
2.17.1
On Wed, Aug 2, 2023 at 5:46 AM Duoming Zhou <[email protected]> wrote:
> The original code puts flush_work() before timer_shutdown_sync()
> in switch_drv_remove(). Although we use flush_work() to stop
> the worker, it could be re-scheduled in switch_timer. As a result,
> the UAF bug will happen. The detail is shown below:
>
> (cpu 0) | (cpu 1)
> switch_drv_remove() |
> flush_work() |
> ... | switch_timer //timer
> | schedule_work(&psw->work)
> timer_shutdown_sync() |
> ... | switch_work_handler //worker
> kfree(psw) //free |
> | psw->state = 0 //use
>
> This patch puts timer_shutdown_sync() before flush_work() to
> mitigate the bugs. As a result, the worker and timer could
> be stopped safely before the deallocate operations.
>
> Fixes: 9f5e8eee5cfe ("sh: generic push-switch framework.")
> Signed-off-by: Duoming Zhou <[email protected]>
Reviewed-by: Geert Uytterhoeven <[email protected]>
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
On Wed, 2023-08-02 at 11:37 +0800, Duoming Zhou wrote:
> The original code puts flush_work() before timer_shutdown_sync()
> in switch_drv_remove(). Although we use flush_work() to stop
> the worker, it could be re-scheduled in switch_timer. As a result,
> the UAF bug will happen. The detail is shown below:
>
> (cpu 0) | (cpu 1)
> switch_drv_remove() |
> flush_work() |
> ... | switch_timer //timer
> | schedule_work(&psw->work)
> timer_shutdown_sync() |
> ... | switch_work_handler //worker
> kfree(psw) //free |
> | psw->state = 0 //use
>
> This patch puts timer_shutdown_sync() before flush_work() to
> mitigate the bugs. As a result, the worker and timer could
> be stopped safely before the deallocate operations.
>
> Fixes: 9f5e8eee5cfe ("sh: generic push-switch framework.")
> Signed-off-by: Duoming Zhou <[email protected]>
> ---
> arch/sh/drivers/push-switch.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/sh/drivers/push-switch.c b/arch/sh/drivers/push-switch.c
> index c95f48ff3f6..6ecba5f521e 100644
> --- a/arch/sh/drivers/push-switch.c
> +++ b/arch/sh/drivers/push-switch.c
> @@ -101,8 +101,8 @@ static int switch_drv_remove(struct platform_device *pdev)
> device_remove_file(&pdev->dev, &dev_attr_switch);
>
> platform_set_drvdata(pdev, NULL);
> - flush_work(&psw->work);
> timer_shutdown_sync(&psw->debounce);
> + flush_work(&psw->work);
> free_irq(irq, pdev);
>
> kfree(psw);
Reviewed-by: John Paul Adrian Glaubitz <[email protected]>
--
.''`. John Paul Adrian Glaubitz
: :' : Debian Developer
`. `' Physicist
`- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913