From: Martin Willi martin@strongswan.org
[ Upstream commit 09db51241118aeb06e1c8cd393b45879ce099b36 ]
On ESP output, sk_wmem_alloc is incremented for the added padding if a socket is associated to the skb. When replying with TCP SYNACKs over IPsec, the associated sk is a casted request socket, only. Increasing sk_wmem_alloc on a request socket results in a write at an arbitrary struct offset. In the best case, this produces the following WARNING:
WARNING: CPU: 1 PID: 0 at lib/refcount.c:102 esp_output_head+0x2e4/0x308 [esp4] refcount_t: addition on 0; use-after-free. CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.0.0-rc3 #2 Hardware name: Marvell Armada 380/385 (Device Tree) [...] [<bf0ff354>] (esp_output_head [esp4]) from [<bf1006a4>] (esp_output+0xb8/0x180 [esp4]) [<bf1006a4>] (esp_output [esp4]) from [<c05dee64>] (xfrm_output_resume+0x558/0x664) [<c05dee64>] (xfrm_output_resume) from [<c05d07b0>] (xfrm4_output+0x44/0xc4) [<c05d07b0>] (xfrm4_output) from [<c05956bc>] (tcp_v4_send_synack+0xa8/0xe8) [<c05956bc>] (tcp_v4_send_synack) from [<c0586ad8>] (tcp_conn_request+0x7f4/0x948) [<c0586ad8>] (tcp_conn_request) from [<c058c404>] (tcp_rcv_state_process+0x2a0/0xe64) [<c058c404>] (tcp_rcv_state_process) from [<c05958ac>] (tcp_v4_do_rcv+0xf0/0x1f4) [<c05958ac>] (tcp_v4_do_rcv) from [<c0598a4c>] (tcp_v4_rcv+0xdb8/0xe20) [<c0598a4c>] (tcp_v4_rcv) from [<c056eb74>] (ip_protocol_deliver_rcu+0x2c/0x2dc) [<c056eb74>] (ip_protocol_deliver_rcu) from [<c056ee6c>] (ip_local_deliver_finish+0x48/0x54) [<c056ee6c>] (ip_local_deliver_finish) from [<c056eecc>] (ip_local_deliver+0x54/0xec) [<c056eecc>] (ip_local_deliver) from [<c056efac>] (ip_rcv+0x48/0xb8) [<c056efac>] (ip_rcv) from [<c0519c2c>] (__netif_receive_skb_one_core+0x50/0x6c) [...]
The issue triggers only when not using TCP syncookies, as for syncookies no socket is associated.
Fixes: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible") Fixes: 03e2a30f6a27 ("esp6: Avoid skb_cow_data whenever possible") Signed-off-by: Martin Willi martin@strongswan.org Signed-off-by: Steffen Klassert steffen.klassert@secunet.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv4/esp4.c | 2 +- net/ipv6/esp6.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c index b00e4a43b4dc..d30285c5d52d 100644 --- a/net/ipv4/esp4.c +++ b/net/ipv4/esp4.c @@ -307,7 +307,7 @@ int esp_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info * skb->len += tailen; skb->data_len += tailen; skb->truesize += tailen; - if (sk) + if (sk && sk_fullsock(sk)) refcount_add(tailen, &sk->sk_wmem_alloc);
goto out; diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c index f112fef79216..ef7822fad0fd 100644 --- a/net/ipv6/esp6.c +++ b/net/ipv6/esp6.c @@ -275,7 +275,7 @@ int esp6_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info skb->len += tailen; skb->data_len += tailen; skb->truesize += tailen; - if (sk) + if (sk && sk_fullsock(sk)) refcount_add(tailen, &sk->sk_wmem_alloc);
goto out;