When the ax25 device is detaching, the ax25_dev_device_down()
calls ax25_ds_del_timer() to cleanup the slave_timer. When
the timer handler is running, the ax25_ds_del_timer() that
calls del_timer() in it will return directly. As a result,
the use-after-free bugs could happen, one of the scenarios
is shown below:
(Thread 1) | (Thread 2)
| ax25_ds_timeout()
ax25_dev_device_down() |
ax25_ds_del_timer() |
del_timer() |
ax25_dev_put() //FREE |
| ax25_dev-> //USE
In order to mitigate bugs, when the device is detaching, use
timer_shutdown_sync() to stop the timer.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Duoming Zhou <[email protected]>
---
Changes in v2:
- Call timer_shutdown_sync() in ax25_dev_device_down().
net/ax25/ax25_dev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c
index c5462486dbc..282ec581c07 100644
--- a/net/ax25/ax25_dev.c
+++ b/net/ax25/ax25_dev.c
@@ -105,7 +105,7 @@ void ax25_dev_device_down(struct net_device *dev)
spin_lock_bh(&ax25_dev_lock);
#ifdef CONFIG_AX25_DAMA_SLAVE
- ax25_ds_del_timer(ax25_dev);
+ timer_shutdown_sync(&ax25_dev->dama.slave_timer);
#endif
/*
--
2.17.1
On Fri, Mar 29, 2024 at 09:50:23AM +0800, Duoming Zhou wrote:
> When the ax25 device is detaching, the ax25_dev_device_down()
> calls ax25_ds_del_timer() to cleanup the slave_timer. When
> the timer handler is running, the ax25_ds_del_timer() that
> calls del_timer() in it will return directly. As a result,
> the use-after-free bugs could happen, one of the scenarios
> is shown below:
>
> (Thread 1) | (Thread 2)
> | ax25_ds_timeout()
> ax25_dev_device_down() |
> ax25_ds_del_timer() |
> del_timer() |
> ax25_dev_put() //FREE |
> | ax25_dev-> //USE
>
> In order to mitigate bugs, when the device is detaching, use
> timer_shutdown_sync() to stop the timer.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Duoming Zhou <[email protected]>
> ---
> Changes in v2:
> - Call timer_shutdown_sync() in ax25_dev_device_down().
Thanks,
as per my review of v1, I do think this is a correct approach to addressing
a valid concern. But I would also value another set of eyes on the problem.
Reviewed-by: Simon Horman <[email protected]>
> net/ax25/ax25_dev.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c
> index c5462486dbc..282ec581c07 100644
> --- a/net/ax25/ax25_dev.c
> +++ b/net/ax25/ax25_dev.c
> @@ -105,7 +105,7 @@ void ax25_dev_device_down(struct net_device *dev)
> spin_lock_bh(&ax25_dev_lock);
>
> #ifdef CONFIG_AX25_DAMA_SLAVE
> - ax25_ds_del_timer(ax25_dev);
> + timer_shutdown_sync(&ax25_dev->dama.slave_timer);
> #endif
>
> /*
> --
> 2.17.1
>
Hello:
This patch was applied to netdev/net.git (main)
by Jakub Kicinski <[email protected]>:
On Fri, 29 Mar 2024 09:50:23 +0800 you wrote:
> When the ax25 device is detaching, the ax25_dev_device_down()
> calls ax25_ds_del_timer() to cleanup the slave_timer. When
> the timer handler is running, the ax25_ds_del_timer() that
> calls del_timer() in it will return directly. As a result,
> the use-after-free bugs could happen, one of the scenarios
> is shown below:
>
> [...]
Here is the summary with links:
- [net,v2] ax25: fix use-after-free bugs caused by ax25_ds_del_timer
https://git.kernel.org/netdev/net/c/fd819ad3ecf6
You are awesome, thank you!
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