Messages in this thread | | | Subject | Re: [PATCH net] tun: fix use after free for ptr_ring | From | Jason Wang <> | Date | Fri, 11 May 2018 09:29:10 +0800 |
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On 2018年05月11日 02:08, Cong Wang wrote: > On Tue, May 8, 2018 at 11:59 PM, Jason Wang <jasowang@redhat.com> wrote: >> We used to initialize ptr_ring during TUNSETIFF, this is because its >> size depends on the tx_queue_len of netdevice. And we try to clean it >> up when socket were detached from netdevice. A race were spotted when >> trying to do uninit during a read which will lead a use after free for >> pointer ring. Solving this by always initialize a zero size ptr_ring >> in open() and do resizing during TUNSETIFF, and then we can safely do >> cleanup during close(). With this, there's no need for the workaround >> that was introduced by commit 4df0bfc79904 ("tun: fix a memory leak >> for tfile->tx_array"). >> > Ah, I didn't know ptr_ring_init(0) could work... Nice patch! > Except one thing below. > > >> diff --git a/drivers/net/tun.c b/drivers/net/tun.c >> index ef33950..298cb96 100644 >> --- a/drivers/net/tun.c >> +++ b/drivers/net/tun.c >> @@ -681,15 +681,6 @@ static void tun_queue_purge(struct tun_file *tfile) >> skb_queue_purge(&tfile->sk.sk_error_queue); >> } >> >> -static void tun_cleanup_tx_ring(struct tun_file *tfile) >> -{ >> - if (tfile->tx_ring.queue) { >> - ptr_ring_cleanup(&tfile->tx_ring, tun_ptr_free); >> - xdp_rxq_info_unreg(&tfile->xdp_rxq); >> - memset(&tfile->tx_ring, 0, sizeof(tfile->tx_ring)); >> - } >> -} > > I don't think you can totally remove ptr_ring_cleanup(), it should be > called unconditionally with your ptr_ring_init(0) trick, right?
Right, my bad. Actually I do intend to cleanup it at close() like what commit log said.
Will send v2.
Thanks
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