| Message ID | 1557199416-55253-1-git-send-email-jasowang@redhat.com |
|---|---|
| State | Superseded |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net] tuntap: synchronize through tfiles array instead of tun->numqueues | expand |
On 5/6/19 11:23 PM, Jason Wang wrote: > When a queue(tfile) is detached through __tun_detach(), we move the > last enabled tfile to the position where detached one sit but don't > NULL out last position. We expect to synchronize the datapath through > tun->numqueues. Unfortunately, this won't work since we're lacking > sufficient mechanism to order or synchronize the access to > tun->numqueues. > > To fix this, NULL out the last position during detaching and check > RCU protected tfile against NULL instead of checking tun->numqueues in > datapath. > > Cc: YueHaibing <yuehaibing@huawei.com> > Cc: Cong Wang <xiyou.wangcong@gmail.com> > Cc: weiyongjun (A) <weiyongjun1@huawei.com> > Fixes: c8d68e6be1c3b ("tuntap: multiqueue support") > Signed-off-by: Jason Wang <jasowang@redhat.com> > --- > drivers/net/tun.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > index e9ca1c0..a64c928 100644 > --- a/drivers/net/tun.c > +++ b/drivers/net/tun.c > @@ -700,6 +700,8 @@ static void __tun_detach(struct tun_file *tfile, bool clean) > tun->tfiles[tun->numqueues - 1]); > ntfile = rtnl_dereference(tun->tfiles[index]); > ntfile->queue_index = index; > + rcu_assign_pointer(tun->tfiles[tun->numqueues - 1], > + NULL); > > --tun->numqueues; > if (clean) { > @@ -1082,7 +1084,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev) > tfile = rcu_dereference(tun->tfiles[txq]); > > /* Drop packet if interface is not attached */ > - if (txq >= tun->numqueues) > + if (!tfile) > goto drop; > > if (!rcu_dereference(tun->steering_prog)) > @@ -1306,13 +1308,13 @@ static int tun_xdp_xmit(struct net_device *dev, int n, > rcu_read_lock(); > > numqueues = READ_ONCE(tun->numqueues); > - if (!numqueues) { > - rcu_read_unlock(); > - return -ENXIO; /* Caller will free/return all frames */ > - } > If you remove the test on (!numqueues), the following might crash with a divide by zero... > tfile = rcu_dereference(tun->tfiles[smp_processor_id() % > numqueues]);
On 2019/5/7 上午11:41, Eric Dumazet wrote: > > On 5/6/19 11:23 PM, Jason Wang wrote: >> When a queue(tfile) is detached through __tun_detach(), we move the >> last enabled tfile to the position where detached one sit but don't >> NULL out last position. We expect to synchronize the datapath through >> tun->numqueues. Unfortunately, this won't work since we're lacking >> sufficient mechanism to order or synchronize the access to >> tun->numqueues. >> >> To fix this, NULL out the last position during detaching and check >> RCU protected tfile against NULL instead of checking tun->numqueues in >> datapath. >> >> Cc: YueHaibing <yuehaibing@huawei.com> >> Cc: Cong Wang <xiyou.wangcong@gmail.com> >> Cc: weiyongjun (A) <weiyongjun1@huawei.com> >> Fixes: c8d68e6be1c3b ("tuntap: multiqueue support") >> Signed-off-by: Jason Wang <jasowang@redhat.com> >> --- >> drivers/net/tun.c | 12 +++++++----- >> 1 file changed, 7 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/net/tun.c b/drivers/net/tun.c >> index e9ca1c0..a64c928 100644 >> --- a/drivers/net/tun.c >> +++ b/drivers/net/tun.c >> @@ -700,6 +700,8 @@ static void __tun_detach(struct tun_file *tfile, bool clean) >> tun->tfiles[tun->numqueues - 1]); >> ntfile = rtnl_dereference(tun->tfiles[index]); >> ntfile->queue_index = index; >> + rcu_assign_pointer(tun->tfiles[tun->numqueues - 1], >> + NULL); >> >> --tun->numqueues; >> if (clean) { >> @@ -1082,7 +1084,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev) >> tfile = rcu_dereference(tun->tfiles[txq]); >> >> /* Drop packet if interface is not attached */ >> - if (txq >= tun->numqueues) >> + if (!tfile) >> goto drop; >> >> if (!rcu_dereference(tun->steering_prog)) >> @@ -1306,13 +1308,13 @@ static int tun_xdp_xmit(struct net_device *dev, int n, >> rcu_read_lock(); >> >> numqueues = READ_ONCE(tun->numqueues); >> - if (!numqueues) { >> - rcu_read_unlock(); >> - return -ENXIO; /* Caller will free/return all frames */ >> - } >> > If you remove the test on (!numqueues), > the following might crash with a divide by zero... Indeed, let me post V2. Thanks > >> tfile = rcu_dereference(tun->tfiles[smp_processor_id() % >> numqueues]);
On 5/6/19 11:54 PM, Jason Wang wrote: > > On 2019/5/7 上午11:41, Eric Dumazet wrote: >> >>> >> If you remove the test on (!numqueues), >> the following might crash with a divide by zero... > > > Indeed, let me post V2. You probably want to fix tun_ebpf_select_queue() as well.
On 2019/5/7 下午10:47, Eric Dumazet wrote: > > On 5/6/19 11:54 PM, Jason Wang wrote: >> On 2019/5/7 上午11:41, Eric Dumazet wrote: >>>> >>> If you remove the test on (!numqueues), >>> the following might crash with a divide by zero... >> >> Indeed, let me post V2. > You probably want to fix tun_ebpf_select_queue() as well. > Yes, will fix this in V3. Thanks
diff --git a/drivers/net/tun.c b/drivers/net/tun.c index e9ca1c0..a64c928 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -700,6 +700,8 @@ static void __tun_detach(struct tun_file *tfile, bool clean) tun->tfiles[tun->numqueues - 1]); ntfile = rtnl_dereference(tun->tfiles[index]); ntfile->queue_index = index; + rcu_assign_pointer(tun->tfiles[tun->numqueues - 1], + NULL); --tun->numqueues; if (clean) { @@ -1082,7 +1084,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev) tfile = rcu_dereference(tun->tfiles[txq]); /* Drop packet if interface is not attached */ - if (txq >= tun->numqueues) + if (!tfile) goto drop; if (!rcu_dereference(tun->steering_prog)) @@ -1306,13 +1308,13 @@ static int tun_xdp_xmit(struct net_device *dev, int n, rcu_read_lock(); numqueues = READ_ONCE(tun->numqueues); - if (!numqueues) { - rcu_read_unlock(); - return -ENXIO; /* Caller will free/return all frames */ - } tfile = rcu_dereference(tun->tfiles[smp_processor_id() % numqueues]); + if (!tfile) { + rcu_read_unlock(); + return -ENXIO; /* Caller will free/return all frames */ + } spin_lock(&tfile->tx_ring.producer_lock); for (i = 0; i < n; i++) {
When a queue(tfile) is detached through __tun_detach(), we move the last enabled tfile to the position where detached one sit but don't NULL out last position. We expect to synchronize the datapath through tun->numqueues. Unfortunately, this won't work since we're lacking sufficient mechanism to order or synchronize the access to tun->numqueues. To fix this, NULL out the last position during detaching and check RCU protected tfile against NULL instead of checking tun->numqueues in datapath. Cc: YueHaibing <yuehaibing@huawei.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: weiyongjun (A) <weiyongjun1@huawei.com> Fixes: c8d68e6be1c3b ("tuntap: multiqueue support") Signed-off-by: Jason Wang <jasowang@redhat.com> --- drivers/net/tun.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)