From: Lin Ma linma@zju.edu.cn
commit 0b9111922b1f399aba6ed1e1b8f2079c3da1aed8 upstream.
There is a possible race condition (use-after-free) like below
(USE) | (FREE) dev_queue_xmit | __dev_queue_xmit | __dev_xmit_skb | sch_direct_xmit | ... xmit_one | netdev_start_xmit | tty_ldisc_kill __netdev_start_xmit | 6pack_close sp_xmit | kfree sp_encaps | |
According to the patch "defer ax25 kfree after unregister_netdev", this patch reorder the kfree after the unregister_netdev to avoid the possible UAF as the unregister_netdev() is well synchronized and won't return if there is a running routine.
Signed-off-by: Lin Ma linma@zju.edu.cn Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/hamradio/6pack.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/drivers/net/hamradio/6pack.c +++ b/drivers/net/hamradio/6pack.c @@ -690,9 +690,11 @@ static void sixpack_close(struct tty_str del_timer_sync(&sp->tx_t); del_timer_sync(&sp->resync_t);
- /* Free all 6pack frame buffers. */ + /* Free all 6pack frame buffers after unreg. */ kfree(sp->rbuff); kfree(sp->xbuff); + + free_netdev(sp->dev); }
/* Perform I/O control on an active 6pack channel. */