xfrm async resumption hold skb->dev refcnt until after transport_finish. However, xfrm_rcv_cb may modify skb->dev to tunnel dev without taking device reference, such as vti_rcv_cb. The subsequent async resumption will decrement the tunnel device's reference count, which lead to uaf of tunnel dev and refcnt leak of orig dev as below: unregister_netdevice: waiting for vti1 to become free. Usage count = -2 Stash the original skb->dev to fix refcnt imbalance. The new skb->dev set by xfrm_rcv_cb can race with device teardown. Extend rcu protection over xfrm_rcv_cb and transport_finish to prevent races. Fixes: 1c428b038400 ("xfrm: hold dev ref until after transport_finish NF_HOOK") Reported-by: Xu Chunxiao Signed-off-by: Dong Chenchen --- changes in v2: - Stash the original skb->dev to fix refcnt imbalance - Extend rcu protection over xfrm_rcv_cb and transport_finish to prevent races. --- net/ipv4/xfrm4_input.c | 2 -- net/ipv6/xfrm6_input.c | 2 -- net/xfrm/xfrm_input.c | 29 ++++++++++++++++------------- 3 files changed, 16 insertions(+), 17 deletions(-) diff --git a/net/ipv4/xfrm4_input.c b/net/ipv4/xfrm4_input.c index c2eac844bcdb..f6f2a8ef3f88 100644 --- a/net/ipv4/xfrm4_input.c +++ b/net/ipv4/xfrm4_input.c @@ -76,8 +76,6 @@ int xfrm4_transport_finish(struct sk_buff *skb, int async) NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, dev_net(dev), NULL, skb, dev, NULL, xfrm4_rcv_encap_finish); - if (async) - dev_put(dev); return 0; } diff --git a/net/ipv6/xfrm6_input.c b/net/ipv6/xfrm6_input.c index 699a001ac166..89d0443b5307 100644 --- a/net/ipv6/xfrm6_input.c +++ b/net/ipv6/xfrm6_input.c @@ -71,8 +71,6 @@ int xfrm6_transport_finish(struct sk_buff *skb, int async) NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, dev_net(dev), NULL, skb, dev, NULL, xfrm6_transport_finish2); - if (async) - dev_put(dev); return 0; } diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c index e4c2cd24936d..eecab337bd0a 100644 --- a/net/xfrm/xfrm_input.c +++ b/net/xfrm/xfrm_input.c @@ -467,6 +467,7 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type) { const struct xfrm_state_afinfo *afinfo; struct net *net = dev_net(skb->dev); + struct net_device *dev = skb->dev; int err; __be32 seq; __be32 seq_hi; @@ -493,7 +494,7 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type) LINUX_MIB_XFRMINSTATEINVALID); if (encap_type == -1) - dev_put(skb->dev); + dev_put(dev); goto drop; } @@ -655,16 +656,16 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type) if (!crypto_done) { spin_unlock(&x->lock); - dev_hold(skb->dev); + dev_hold(dev); nexthdr = x->type->input(x, skb); if (nexthdr == -EINPROGRESS) { if (async) - dev_put(skb->dev); + dev_put(dev); return 0; } - dev_put(skb->dev); + dev_put(dev); spin_lock(&x->lock); } resume: @@ -699,7 +700,7 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type) err = xfrm_inner_mode_input(x, skb); if (err == -EINPROGRESS) { if (async) - dev_put(skb->dev); + dev_put(dev); return 0; } else if (err) { XFRM_INC_STATS(net, LINUX_MIB_XFRMINSTATEMODEERROR); @@ -726,9 +727,12 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type) crypto_done = false; } while (!err); + rcu_read_lock(); err = xfrm_rcv_cb(skb, family, x->type->proto, 0); - if (err) + if (err) { + rcu_read_unlock(); goto drop; + } nf_reset_ct(skb); @@ -739,8 +743,9 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type) if (skb_valid_dst(skb)) skb_dst_drop(skb); if (async) - dev_put(skb->dev); + dev_put(dev); gro_cells_receive(&gro_cells, skb); + rcu_read_unlock(); return 0; } else { xo = xfrm_offload(skb); @@ -748,23 +753,21 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type) xfrm_gro = xo->flags & XFRM_GRO; err = -EAFNOSUPPORT; - rcu_read_lock(); afinfo = xfrm_state_afinfo_get_rcu(x->props.family); if (likely(afinfo)) err = afinfo->transport_finish(skb, xfrm_gro || async); - rcu_read_unlock(); if (xfrm_gro) { sp = skb_sec_path(skb); if (sp) sp->olen = 0; if (skb_valid_dst(skb)) skb_dst_drop(skb); - if (async) - dev_put(skb->dev); gro_cells_receive(&gro_cells, skb); - return err; } + if (async) + dev_put(dev); + rcu_read_unlock(); return err; } @@ -772,7 +775,7 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type) spin_unlock(&x->lock); drop: if (async) - dev_put(skb->dev); + dev_put(dev); xfrm_rcv_cb(skb, family, x && x->type ? x->type->proto : nexthdr, -1); kfree_skb(skb); return 0; -- 2.25.1