• Martin Willi's avatar
    esp: Skip TX bytes accounting when sending from a request socket · 09db5124
    Martin Willi authored
    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: cac2661c ("esp4: Avoid skb_cow_data whenever possible")
    Fixes: 03e2a30f ("esp6: Avoid skb_cow_data whenever possible")
    Signed-off-by: default avatarMartin Willi <martin@strongswan.org>
    Signed-off-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
    09db5124
esp6.c 22 KB