Commit 60aa3b08 authored Jan 05, 2016 by One Thousand Gnomes Committed by David S. Miller Jan 06, 2016

6pack: fix free memory scribbles



commit acf673a3 fixed a user triggerable free
memory scribble but in doing so replaced it with a different one that allows
the user to control the data and scribble even more.

sixpack_close is called by the tty layer in tty context. The tty context is
protected by sp_get() and sp_put(). However network layer activity via
sp_xmit() is not protected this way. We must therefore stop the queue
otherwise the user gets to dump a buffer mostly of their choice into freed
kernel pages.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 55795ef5

drivers/net/hamradio/6pack.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -683,6 +683,12 @@ static void sixpack_close(struct tty_struct *tty)
		if (!atomic_dec_and_test(&sp->refcnt))
		down(&sp->dead_sem);

		/* We must stop the queue to avoid potentially scribbling
		* on the free buffers. The sp->dead_sem is not sufficient
		* to protect us from sp->xbuff access.
		*/
		netif_stop_queue(sp->dev);

		del_timer_sync(&sp->tx_t);
		del_timer_sync(&sp->resync_t);