Re: [PATCH net] tuntap: correctly wake up process during uninit
From: Jason Wang <hidden>
Date: 2016-05-19 05:35:12
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On 2016年05月18日 21:01, Eric Dumazet wrote:
On Wed, 2016-05-18 at 18:58 +0800, Jason Wang wrote:quoted
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")<nit : no newline before Fixes: and other parts>
Ok.
quoted hunk ↗ jump to hunk
Cc: Eric Dumazet <edumazet@google.com> Cc: Xi Wang <redacted> Cc: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Jason Wang <redacted> --- The patch is needed for -stable. --- drivers/net/tun.c | 3 +++ 1 file changed, 3 insertions(+)diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 425e983..752d849 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c@@ -580,11 +580,13 @@ 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); }@@ -641,6 +643,7 @@ 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++;Is the "if (tun->dev->reg_state != NETREG_REGISTERED) return -EIO;" check still needed then ? Thanks.
No need since we've check tun before, will remove this in V2. Thanks