Re: Re: [PATCH v0] hamradio: delete unnecessary free_netdev()

Hi Jakub

On Thu, 11 Nov 2021 22:00:07 +0800 Lin Ma wrote:

quoted

The former patch "defer 6pack kfree after unregister_netdev" adds
free_netdev() function in sixpack_close(), which is a bad copy from the
similar code in mkiss_close(). However, this free is unnecessary as the
flag needs_free_netdev is set to true in sp_setup(), hence the
unregister_netdev() will free the netdev automatically.

Signed-off-by: Lin Ma <redacted>
---
 drivers/net/hamradio/6pack.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
index bfdf89e54752..180c8f08169b 100644
--- a/drivers/net/hamradio/6pack.c
+++ b/drivers/net/hamradio/6pack.c

@@ -677,8 +677,6 @@ static void sixpack_close(struct tty_struct *tty)
 	/* Free all 6pack frame buffers after unreg. */
 	kfree(sp->rbuff);
 	kfree(sp->xbuff);
-
-	free_netdev(sp->dev);

sp is netdev_priv() tho, so this is now a UAF. I'd go for removing the
needs_free_netdev = true instead.

quoted

 }
 
 /* Perform I/O control on an active 6pack channel. */

Okay, that make senses, wait a minute.

Thanks
Lin