| From foo@baz Thu Mar 28 21:57:57 CET 2019 |
| From: Eric Dumazet <edumazet@google.com> |
| Date: Thu, 14 Mar 2019 20:19:47 -0700 |
| Subject: tun: properly test for IFF_UP |
| |
| From: Eric Dumazet <edumazet@google.com> |
| |
| [ Upstream commit 4477138fa0ae4e1b699786ef0600863ea6e6c61c ] |
| |
| Same reasons than the ones explained in commit 4179cb5a4c92 |
| ("vxlan: test dev->flags & IFF_UP before calling netif_rx()") |
| |
| netif_rx_ni() or napi_gro_frags() must be called under a strict contract. |
| |
| At device dismantle phase, core networking clears IFF_UP |
| and flush_all_backlogs() is called after rcu grace period |
| to make sure no incoming packet might be in a cpu backlog |
| and still referencing the device. |
| |
| A similar protocol is used for gro layer. |
| |
| Most drivers call netif_rx() from their interrupt handler, |
| and since the interrupts are disabled at device dismantle, |
| netif_rx() does not have to check dev->flags & IFF_UP |
| |
| Virtual drivers do not have this guarantee, and must |
| therefore make the check themselves. |
| |
| Fixes: 1bd4978a88ac ("tun: honor IFF_UP in tun_get_user()") |
| Signed-off-by: Eric Dumazet <edumazet@google.com> |
| Reported-by: syzbot <syzkaller@googlegroups.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| drivers/net/tun.c | 15 +++++++++++---- |
| 1 file changed, 11 insertions(+), 4 deletions(-) |
| |
| --- a/drivers/net/tun.c |
| +++ b/drivers/net/tun.c |
| @@ -1403,9 +1403,6 @@ static ssize_t tun_get_user(struct tun_s |
| u32 rxhash; |
| int skb_xdp = 1; |
| |
| - if (!(tun->dev->flags & IFF_UP)) |
| - return -EIO; |
| - |
| if (!(tun->flags & IFF_NO_PI)) { |
| if (len < sizeof(pi)) |
| return -EINVAL; |
| @@ -1493,9 +1490,11 @@ static ssize_t tun_get_user(struct tun_s |
| err = skb_copy_datagram_from_iter(skb, 0, from, len); |
| |
| if (err) { |
| + err = -EFAULT; |
| +drop: |
| this_cpu_inc(tun->pcpu_stats->rx_dropped); |
| kfree_skb(skb); |
| - return -EFAULT; |
| + return err; |
| } |
| } |
| |
| @@ -1566,11 +1565,19 @@ static ssize_t tun_get_user(struct tun_s |
| } |
| |
| rxhash = __skb_get_hash_symmetric(skb); |
| + |
| + rcu_read_lock(); |
| + if (unlikely(!(tun->dev->flags & IFF_UP))) { |
| + err = -EIO; |
| + goto drop; |
| + } |
| + |
| #ifndef CONFIG_4KSTACKS |
| tun_rx_batched(tun, tfile, skb, more); |
| #else |
| netif_rx_ni(skb); |
| #endif |
| + rcu_read_unlock(); |
| |
| stats = get_cpu_ptr(tun->pcpu_stats); |
| u64_stats_update_begin(&stats->syncp); |