commit acf673a3187edf72068ee2f92f4dc47d66baed47 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 <[email protected]> --- drivers/net/hamradio/6pack.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c index 9f0b1c3..b3ba6a8 100644 --- a/drivers/net/hamradio/6pack.c +++ b/drivers/net/hamradio/6pack.c @@ -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); -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
