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hamradio: remove needs_free_netdev to avoid UAF 

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: 0b9111922b ("hamradio: defer 6pack kfree after unregister_netdev")
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Link: https://lore.kernel.org/r/20211111141402.7551-1-linma@zju.edu.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Lin Ma 2021-11-11 22:14:02 +08:00 committed by Jakub Kicinski
parent 66f4beaa6c
commit 81b1d548d0
1 changed files with 0 additions and 1 deletions
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1
drivers/net/hamradio/6pack.c
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@ -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;