From: Jason Wang Date: Thu, 19 May 2016 05:36:51 +0000 (+0800) Subject: tuntap: correctly wake up process during uninit X-Git-Tag: v3.16.37~194 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=c56ec947ccea7ee9270a8ee8b40f45f1810a3720;p=thirdparty%2Fkernel%2Fstable.git tuntap: correctly wake up process during uninit commit addf8fc4acb1cf79492ac64966f07178793cb3d7 upstream. We used to check dev->reg_state against NETREG_REGISTERED after each time we are woke up. But after commit 9e641bdcfa4e ("net-tun: restructure tun_do_read for better sleep/wakeup efficiency"), it uses skb_recv_datagram() which does not check dev->reg_state. This will result if we delete a tun/tap device after a process is blocked in the reading. The device will wait for the reference count which was held by that process for ever. Fixes this by using RCV_SHUTDOWN which will be checked during sk_recv_datagram() before trying to wake up the process during uninit. Fixes: 9e641bdcfa4e ("net-tun: restructure tun_do_read for better sleep/wakeup efficiency") Cc: Eric Dumazet Cc: Xi Wang Cc: Michael S. Tsirkin Signed-off-by: Jason Wang Acked-by: Eric Dumazet Acked-by: Michael S. Tsirkin Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 999484feb3777..4d4527c13f527 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -499,11 +499,13 @@ static void tun_detach_all(struct net_device *dev) for (i = 0; i < n; i++) { tfile = rtnl_dereference(tun->tfiles[i]); BUG_ON(!tfile); + tfile->socket.sk->sk_shutdown = RCV_SHUTDOWN; tfile->socket.sk->sk_data_ready(tfile->socket.sk); RCU_INIT_POINTER(tfile->tun, NULL); --tun->numqueues; } list_for_each_entry(tfile, &tun->disabled, next) { + tfile->socket.sk->sk_shutdown = RCV_SHUTDOWN; tfile->socket.sk->sk_data_ready(tfile->socket.sk); RCU_INIT_POINTER(tfile->tun, NULL); } @@ -559,6 +561,7 @@ static int tun_attach(struct tun_struct *tun, struct file *file, bool skip_filte goto out; } tfile->queue_index = tun->numqueues; + tfile->socket.sk->sk_shutdown &= ~RCV_SHUTDOWN; rcu_assign_pointer(tfile->tun, tun); rcu_assign_pointer(tun->tfiles[tun->numqueues], tfile); tun->numqueues++; @@ -1345,9 +1348,6 @@ static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile, if (!len) return ret; - if (tun->dev->reg_state != NETREG_REGISTERED) - return -EIO; - /* Read frames from queue */ skb = __skb_recv_datagram(tfile->socket.sk, noblock ? MSG_DONTWAIT : 0, &peeked, &off, &err);