The former patch "defer 6pack kfree after unregister_netdev" reorders
the kfree of two buffer after the unregister_netdev to prevent the race
condition. It also adds free_netdev() function in sixpack_close(), which
is a direct copy from the similar code in mkiss_close().
However, in sixpack driver, the flag needs_free_netdev is set to true in
sp_setup(), hence the unregister_netdev() will free the netdev
automatically. Therefore, as the sp is netdev_priv, use-after-free
occurs.
This patch removes the needs_free_netdev = true and just let the
free_netdev to finish this deallocation task.
Signed-off-by: Lin Ma <[email protected]>
---
drivers/net/hamradio/6pack.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
index bfdf89e54752..8a19a06b505d 100644
--- a/drivers/net/hamradio/6pack.c
+++ b/drivers/net/hamradio/6pack.c
@@ -306,7 +306,6 @@ static void sp_setup(struct net_device *dev)
{
/* Finish setting up the DEVICE info. */
dev->netdev_ops = &sp_netdev_ops;
- dev->needs_free_netdev = true;
dev->mtu = SIXP_MTU;
dev->hard_header_len = AX25_MAX_HEADER_LEN;
dev->header_ops = &ax25_header_ops;
--
2.33.1
On Thu, 11 Nov 2021 22:14:02 +0800 Lin Ma wrote:
> The former patch "defer 6pack kfree after unregister_netdev" reorders
> the kfree of two buffer after the unregister_netdev to prevent the race
> condition. It also adds free_netdev() function in sixpack_close(), which
> is a direct copy from the similar code in mkiss_close().
>
> However, in sixpack driver, the flag needs_free_netdev is set to true in
> sp_setup(), hence the unregister_netdev() will free the netdev
> automatically. Therefore, as the sp is netdev_priv, use-after-free
> occurs.
>
> This patch removes the needs_free_netdev = true and just let the
> free_netdev to finish this deallocation task.
>
> Signed-off-by: Lin Ma <[email protected]>
Fixes: 0b9111922b1f ("hamradio: defer 6pack kfree after unregister_netdev")
Hello:
This patch was applied to netdev/net.git (master)
by Jakub Kicinski <[email protected]>:
On Thu, 11 Nov 2021 22:14:02 +0800 you wrote:
> The former patch "defer 6pack kfree after unregister_netdev" reorders
> the kfree of two buffer after the unregister_netdev to prevent the race
> condition. It also adds free_netdev() function in sixpack_close(), which
> is a direct copy from the similar code in mkiss_close().
>
> However, in sixpack driver, the flag needs_free_netdev is set to true in
> sp_setup(), hence the unregister_netdev() will free the netdev
> automatically. Therefore, as the sp is netdev_priv, use-after-free
> occurs.
>
> [...]
Here is the summary with links:
- [v1] hamradio: remove needs_free_netdev to avoid UAF
https://git.kernel.org/netdev/net/c/81b1d548d00b
You are awesome, thank you!
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