This is a note to let you know that I've just added the patch titled hamradio: remove needs_free_netdev to avoid UAF to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: hamradio-remove-needs_free_netdev-to-avoid-uaf.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 81b1d548d00bcd028303c4f3150fa753b9b8aa71 Mon Sep 17 00:00:00 2001 From: Lin Ma <linma@xxxxxxxxxx> Date: Thu, 11 Nov 2021 22:14:02 +0800 Subject: hamradio: remove needs_free_netdev to avoid UAF From: Lin Ma <linma@xxxxxxxxxx> commit 81b1d548d00bcd028303c4f3150fa753b9b8aa71 upstream. 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. Fixes: 0b9111922b1f ("hamradio: defer 6pack kfree after unregister_netdev") Signed-off-by: Lin Ma <linma@xxxxxxxxxx> Link: https://lore.kernel.org/r/20211111141402.7551-1-linma@xxxxxxxxxx Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Signed-off-by: Ovidiu Panait <ovidiu.panait@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/net/hamradio/6pack.c | 1 - 1 file changed, 1 deletion(-) --- a/drivers/net/hamradio/6pack.c +++ b/drivers/net/hamradio/6pack.c @@ -311,7 +311,6 @@ static void sp_setup(struct net_device * { /* 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; Patches currently in stable-queue which might be from linma@xxxxxxxxxx are queue-4.19/hamradio-remove-needs_free_netdev-to-avoid-uaf.patch queue-4.19/hamradio-defer-6pack-kfree-after-unregister_netdev.patch