From: Jason Wang jasowang@redhat.com

commit b196d88aba8ac72b775137854121097f4c4c6862 upstream.

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").

Backport Note :- Comparison with the upstream patch: [1] A "semantic revert" of the changes made in 4df0bfc799("tun: fix a memory leak for tfile->tx_array"). 4df0bfc799 was applied upstream, and then skb array was changed to use ptr_ring. The upstream patch then removes the changes introduced by 4df0bfc799. This backport does the same; "revert" the changes made by 4df0bfc799. [2] xdp_rxq_info_unreg() being called in relevant locations As xdp_rxq_info related patches are not present in 4.14, these changes are not needed in the backport. [3] An instance of ptr_ring_init needs to be replaced by skb_array_init Inside tun_attach() [4] ptr_ring_cleanup needs to be replaced by skb_array_cleanup Inside tun_chr_close()

Note that the backport for 7063efd33b ("tuntap: fix use after free during release") needs to be applied on top of this patch.

Reported-by: syzbot+e8b902c3c3fadf0a9dba@syzkaller.appspotmail.com Cc: Eric Dumazet eric.dumazet@gmail.com Cc: Cong Wang xiyou.wangcong@gmail.com Cc: Michael S. Tsirkin mst@redhat.com Fixes: 1576d9860599 ("tun: switch to use skb array for tx") Signed-off-by: Jason Wang jasowang@redhat.com Acked-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Zubin Mithra zsm@chromium.org --- drivers/net/tun.c | 21 +++++++-------------- 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c index cb17ffadfc30..87a989be1cef 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -534,14 +534,6 @@ static void tun_queue_purge(struct tun_file *tfile) skb_queue_purge(&tfile->sk.sk_error_queue); }

-static void tun_cleanup_tx_array(struct tun_file *tfile) -{ - if (tfile->tx_array.ring.queue) { - skb_array_cleanup(&tfile->tx_array); - memset(&tfile->tx_array, 0, sizeof(tfile->tx_array)); - } -} - static void __tun_detach(struct tun_file *tfile, bool clean) { struct tun_file *ntfile; @@ -583,7 +575,6 @@ static void __tun_detach(struct tun_file *tfile, bool clean) tun->dev->reg_state == NETREG_REGISTERED) unregister_netdevice(tun->dev); } - tun_cleanup_tx_array(tfile); sock_put(&tfile->sk); } } @@ -623,13 +614,11 @@ static void tun_detach_all(struct net_device *dev) /* Drop read queue */ tun_queue_purge(tfile); sock_put(&tfile->sk); - tun_cleanup_tx_array(tfile); } list_for_each_entry_safe(tfile, tmp, &tun->disabled, next) { tun_enable_queue(tfile); tun_queue_purge(tfile); sock_put(&tfile->sk); - tun_cleanup_tx_array(tfile); } BUG_ON(tun->numdisabled != 0);

@@ -675,7 +664,7 @@ static int tun_attach(struct tun_struct *tun, struct file *file, bool skip_filte }

if (!tfile->detached && - skb_array_init(&tfile->tx_array, dev->tx_queue_len, GFP_KERNEL)) { + skb_array_resize(&tfile->tx_array, dev->tx_queue_len, GFP_KERNEL)) { err = -ENOMEM; goto out; } @@ -2624,6 +2613,11 @@ static int tun_chr_open(struct inode *inode, struct file * file) &tun_proto, 0); if (!tfile) return -ENOMEM; + if (skb_array_init(&tfile->tx_array, 0, GFP_KERNEL)) { + sk_free(&tfile->sk); + return -ENOMEM; + } + RCU_INIT_POINTER(tfile->tun, NULL); tfile->flags = 0; tfile->ifindex = 0; @@ -2644,8 +2638,6 @@ static int tun_chr_open(struct inode *inode, struct file * file)

sock_set_flag(&tfile->sk, SOCK_ZEROCOPY);

- memset(&tfile->tx_array, 0, sizeof(tfile->tx_array)); - return 0; }

@@ -2654,6 +2646,7 @@ static int tun_chr_close(struct inode *inode, struct file *file) struct tun_file *tfile = file->private_data;

tun_detach(tfile, true); + skb_array_cleanup(&tfile->tx_array);

return 0; }