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    Subject[PATCH AUTOSEL 4.19 04/48] esp: Skip TX bytes accounting when sending from a request socket
    Date
    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 97689012b357..12a43a5369a5 100644
    --- a/net/ipv4/esp4.c
    +++ b/net/ipv4/esp4.c
    @@ -325,7 +325,7 @@ 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 88a7579c23bd..a7d996148eed 100644
    --- a/net/ipv6/esp6.c
    +++ b/net/ipv6/esp6.c
    @@ -293,7 +293,7 @@ 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;
    --
    2.19.1
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