• Eric Dumazet's avatar
    tcp: add tcp_v4_fill_cb()/tcp_v4_restore_cb() · eeea10b8
    Eric Dumazet authored
    James Morris reported kernel stack corruption bug [1] while
    running the SELinux testsuite, and bisected to a recent
    commit bffa72cf ("net: sk_buff rbnode reorg")
    
    We believe this commit is fine, but exposes an older bug.
    
    SELinux code runs from tcp_filter() and might send an ICMP,
    expecting IP options to be found in skb->cb[] using regular IPCB placement.
    
    We need to defer TCP mangling of skb->cb[] after tcp_filter() calls.
    
    This patch adds tcp_v4_fill_cb()/tcp_v4_restore_cb() in a very
    similar way we added them for IPv6.
    
    [1]
    [  339.806024] SELinux: failure in selinux_parse_skb(), unable to parse packet
    [  339.822505] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffff81745af5
    [  339.822505]
    [  339.852250] CPU: 4 PID: 3642 Comm: client Not tainted 4.15.0-rc1-test #15
    [  339.868498] Hardware name: LENOVO 10FGS0VA1L/30BC, BIOS FWKT68A   01/19/2017
    [  339.885060] Call Trace:
    [  339.896875]  <IRQ>
    [  339.908103]  dump_stack+0x63/0x87
    [  339.920645]  panic+0xe8/0x248
    [  339.932668]  ? ip_push_pending_frames+0x33/0x40
    [  339.946328]  ? icmp_send+0x525/0x530
    [  339.958861]  ? kfree_skbmem+0x60/0x70
    [  339.971431]  __stack_chk_fail+0x1b/0x20
    [  339.984049]  icmp_send+0x525/0x530
    [  339.996205]  ? netlbl_skbuff_err+0x36/0x40
    [  340.008997]  ? selinux_netlbl_err+0x11/0x20
    [  340.021816]  ? selinux_socket_sock_rcv_skb+0x211/0x230
    [  340.035529]  ? security_sock_rcv_skb+0x3b/0x50
    [  340.048471]  ? sk_filter_trim_cap+0x44/0x1c0
    [  340.061246]  ? tcp_v4_inbound_md5_hash+0x69/0x1b0
    [  340.074562]  ? tcp_filter+0x2c/0x40
    [  340.086400]  ? tcp_v4_rcv+0x820/0xa20
    [  340.098329]  ? ip_local_deliver_finish+0x71/0x1a0
    [  340.111279]  ? ip_local_deliver+0x6f/0xe0
    [  340.123535]  ? ip_rcv_finish+0x3a0/0x3a0
    [  340.135523]  ? ip_rcv_finish+0xdb/0x3a0
    [  340.147442]  ? ip_rcv+0x27c/0x3c0
    [  340.158668]  ? inet_del_offload+0x40/0x40
    [  340.170580]  ? __netif_receive_skb_core+0x4ac/0x900
    [  340.183285]  ? rcu_accelerate_cbs+0x5b/0x80
    [  340.195282]  ? __netif_receive_skb+0x18/0x60
    [  340.207288]  ? process_backlog+0x95/0x140
    [  340.218948]  ? net_rx_action+0x26c/0x3b0
    [  340.230416]  ? __do_softirq+0xc9/0x26a
    [  340.241625]  ? do_softirq_own_stack+0x2a/0x40
    [  340.253368]  </IRQ>
    [  340.262673]  ? do_softirq+0x50/0x60
    [  340.273450]  ? __local_bh_enable_ip+0x57/0x60
    [  340.285045]  ? ip_finish_output2+0x175/0x350
    [  340.296403]  ? ip_finish_output+0x127/0x1d0
    [  340.307665]  ? nf_hook_slow+0x3c/0xb0
    [  340.318230]  ? ip_output+0x72/0xe0
    [  340.328524]  ? ip_fragment.constprop.54+0x80/0x80
    [  340.340070]  ? ip_local_out+0x35/0x40
    [  340.350497]  ? ip_queue_xmit+0x15c/0x3f0
    [  340.361060]  ? __kmalloc_reserve.isra.40+0x31/0x90
    [  340.372484]  ? __skb_clone+0x2e/0x130
    [  340.382633]  ? tcp_transmit_skb+0x558/0xa10
    [  340.393262]  ? tcp_connect+0x938/0xad0
    [  340.403370]  ? ktime_get_with_offset+0x4c/0xb0
    [  340.414206]  ? tcp_v4_connect+0x457/0x4e0
    [  340.424471]  ? __inet_stream_connect+0xb3/0x300
    [  340.435195]  ? inet_stream_connect+0x3b/0x60
    [  340.445607]  ? SYSC_connect+0xd9/0x110
    [  340.455455]  ? __audit_syscall_entry+0xaf/0x100
    [  340.466112]  ? syscall_trace_enter+0x1d0/0x2b0
    [  340.476636]  ? __audit_syscall_exit+0x209/0x290
    [  340.487151]  ? SyS_connect+0xe/0x10
    [  340.496453]  ? do_syscall_64+0x67/0x1b0
    [  340.506078]  ? entry_SYSCALL64_slow_path+0x25/0x25
    
    Fixes: 971f10ec ("tcp: better TCP_SKB_CB layout to reduce cache line misses")
    Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
    Reported-by: default avatarJames Morris <james.l.morris@oracle.com>
    Tested-by: default avatarJames Morris <james.l.morris@oracle.com>
    Tested-by: default avatarCasey Schaufler <casey@schaufler-ca.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    eeea10b8
tcp_ipv4.c 66.3 KB