4.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: Eric Dumazet <[email protected]> [ 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 <[email protected]> Reported-by: syzbot <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- drivers/net/tun.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1194,9 +1194,6 @@ static ssize_t tun_get_user(struct tun_s u32 rxhash; ssize_t n; - if (!(tun->dev->flags & IFF_UP)) - return -EIO; - if (!(tun->flags & IFF_NO_PI)) { if (len < sizeof(pi)) return -EINVAL; @@ -1273,9 +1270,11 @@ 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; } err = virtio_net_hdr_to_skb(skb, &gso, tun_is_little_endian(tun)); @@ -1327,7 +1326,15 @@ static ssize_t tun_get_user(struct tun_s skb_probe_transport_header(skb, 0); rxhash = skb_get_hash(skb); + + rcu_read_lock(); + if (unlikely(!(tun->dev->flags & IFF_UP))) { + err = -EIO; + goto drop; + } + netif_rx_ni(skb); + rcu_read_unlock(); stats = get_cpu_ptr(tun->pcpu_stats); u64_stats_update_begin(&stats->syncp);
