| From | Ben Hutchings <> | Date | Sat, 13 Aug 2016 18:42:51 +0100 | Subject | [PATCH 3.16 110/305] tuntap: correctly wake up process during uninit |
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3.16.37-rc1 review patch. If anyone has any objections, please let me know.
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From: Jason Wang <jasowang@redhat.com>
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 <edumazet@google.com> Cc: Xi Wang <xii@google.com> Cc: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Jason Wang <jasowang@redhat.com> Acked-by: Eric Dumazet <edumazet@google.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- drivers/net/tun.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -499,11 +499,13 @@ static void tun_detach_all(struct net_de 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 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_st 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);
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