From b196d88aba8ac72b775137854121097f4c4c6862 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Fri, 11 May 2018 10:49:25 +0800 Subject: [PATCH] tun: fix use after free for ptr_ring 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"). Reported-by: syzbot+e8b902c3c3fadf0a9dba@syzkaller.appspotmail.com Cc: Eric Dumazet Cc: Cong Wang Cc: Michael S. Tsirkin Fixes: 1576d9860599 ("tun: switch to use skb array for tx") Signed-off-by: Jason Wang Acked-by: Michael S. Tsirkin Signed-off-by: David S. Miller --- drivers/net/tun.c | 27 ++++++++++++--------------- 1 file changed, 12 insertions(+), 15 deletions(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index ef33950a45d9..9fbbb328b95b 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)); - } -} - static void __tun_detach(struct tun_file *tfile, bool clean) { struct tun_file *ntfile; @@ -736,7 +727,8 @@ static void __tun_detach(struct tun_file *tfile, bool clean) tun->dev->reg_state == NETREG_REGISTERED) unregister_netdevice(tun->dev); } - tun_cleanup_tx_ring(tfile); + if (tun) + xdp_rxq_info_unreg(&tfile->xdp_rxq); sock_put(&tfile->sk); } } @@ -783,14 +775,14 @@ static void tun_detach_all(struct net_device *dev) tun_napi_del(tun, tfile); /* Drop read queue */ tun_queue_purge(tfile); + xdp_rxq_info_unreg(&tfile->xdp_rxq); sock_put(&tfile->sk); - tun_cleanup_tx_ring(tfile); } list_for_each_entry_safe(tfile, tmp, &tun->disabled, next) { tun_enable_queue(tfile); tun_queue_purge(tfile); + xdp_rxq_info_unreg(&tfile->xdp_rxq); sock_put(&tfile->sk); - tun_cleanup_tx_ring(tfile); } BUG_ON(tun->numdisabled != 0); @@ -834,7 +826,8 @@ static int tun_attach(struct tun_struct *tun, struct file *file, } if (!tfile->detached && - ptr_ring_init(&tfile->tx_ring, dev->tx_queue_len, GFP_KERNEL)) { + ptr_ring_resize(&tfile->tx_ring, dev->tx_queue_len, + GFP_KERNEL, tun_ptr_free)) { err = -ENOMEM; goto out; } @@ -3219,6 +3212,11 @@ static int tun_chr_open(struct inode *inode, struct file * file) &tun_proto, 0); if (!tfile) return -ENOMEM; + if (ptr_ring_init(&tfile->tx_ring, 0, GFP_KERNEL)) { + sk_free(&tfile->sk); + return -ENOMEM; + } + RCU_INIT_POINTER(tfile->tun, NULL); tfile->flags = 0; tfile->ifindex = 0; @@ -3239,8 +3237,6 @@ static int tun_chr_open(struct inode *inode, struct file * file) sock_set_flag(&tfile->sk, SOCK_ZEROCOPY); - memset(&tfile->tx_ring, 0, sizeof(tfile->tx_ring)); - return 0; } @@ -3249,6 +3245,7 @@ static int tun_chr_close(struct inode *inode, struct file *file) struct tun_file *tfile = file->private_data; tun_detach(tfile, true); + ptr_ring_cleanup(&tfile->tx_ring, tun_ptr_free); return 0; }