• Taehee Yoo's avatar
    ip: frags: fix crash in ip_do_fragment() · 5d407b07
    Taehee Yoo authored
    A kernel crash occurrs when defragmented packet is fragmented
    in ip_do_fragment().
    In defragment routine, skb_orphan() is called and
    skb->ip_defrag_offset is set. but skb->sk and
    skb->ip_defrag_offset are same union member. so that
    frag->sk is not NULL.
    Hence crash occurrs in skb->sk check routine in ip_do_fragment() when
    defragmented packet is fragmented.
    
    test commands:
       %iptables -t nat -I POSTROUTING -j MASQUERADE
       %hping3 192.168.4.2 -s 1000 -p 2000 -d 60000
    
    splat looks like:
    [  261.069429] kernel BUG at net/ipv4/ip_output.c:636!
    [  261.075753] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
    [  261.083854] CPU: 1 PID: 1349 Comm: hping3 Not tainted 4.19.0-rc2+ #3
    [  261.100977] RIP: 0010:ip_do_fragment+0x1613/0x2600
    [  261.106945] Code: e8 e2 38 e3 fe 4c 8b 44 24 18 48 8b 74 24 08 e9 92 f6 ff ff 80 3c 02 00 0f 85 da 07 00 00 48 8b b5 d0 00 00 00 e9 25 f6 ff ff <0f> 0b 0f 0b 44 8b 54 24 58 4c 8b 4c 24 18 4c 8b 5c 24 60 4c 8b 6c
    [  261.127015] RSP: 0018:ffff8801031cf2c0 EFLAGS: 00010202
    [  261.134156] RAX: 1ffff1002297537b RBX: ffffed0020639e6e RCX: 0000000000000004
    [  261.142156] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff880114ba9bd8
    [  261.150157] RBP: ffff880114ba8a40 R08: ffffed0022975395 R09: ffffed0022975395
    [  261.158157] R10: 0000000000000001 R11: ffffed0022975394 R12: ffff880114ba9ca4
    [  261.166159] R13: 0000000000000010 R14: ffff880114ba9bc0 R15: dffffc0000000000
    [  261.174169] FS:  00007fbae2199700(0000) GS:ffff88011b400000(0000) knlGS:0000000000000000
    [  261.183012] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    [  261.189013] CR2: 00005579244fe000 CR3: 0000000119bf4000 CR4: 00000000001006e0
    [  261.198158] Call Trace:
    [  261.199018]  ? dst_output+0x180/0x180
    [  261.205011]  ? save_trace+0x300/0x300
    [  261.209018]  ? ip_copy_metadata+0xb00/0xb00
    [  261.213034]  ? sched_clock_local+0xd4/0x140
    [  261.218158]  ? kill_l4proto+0x120/0x120 [nf_conntrack]
    [  261.223014]  ? rt_cpu_seq_stop+0x10/0x10
    [  261.227014]  ? find_held_lock+0x39/0x1c0
    [  261.233008]  ip_finish_output+0x51d/0xb50
    [  261.237006]  ? ip_fragment.constprop.56+0x220/0x220
    [  261.243011]  ? nf_ct_l4proto_register_one+0x5b0/0x5b0 [nf_conntrack]
    [  261.250152]  ? rcu_is_watching+0x77/0x120
    [  261.255010]  ? nf_nat_ipv4_out+0x1e/0x2b0 [nf_nat_ipv4]
    [  261.261033]  ? nf_hook_slow+0xb1/0x160
    [  261.265007]  ip_output+0x1c7/0x710
    [  261.269005]  ? ip_mc_output+0x13f0/0x13f0
    [  261.273002]  ? __local_bh_enable_ip+0xe9/0x1b0
    [  261.278152]  ? ip_fragment.constprop.56+0x220/0x220
    [  261.282996]  ? nf_hook_slow+0xb1/0x160
    [  261.287007]  raw_sendmsg+0x21f9/0x4420
    [  261.291008]  ? dst_output+0x180/0x180
    [  261.297003]  ? sched_clock_cpu+0x126/0x170
    [  261.301003]  ? find_held_lock+0x39/0x1c0
    [  261.306155]  ? stop_critical_timings+0x420/0x420
    [  261.311004]  ? check_flags.part.36+0x450/0x450
    [  261.315005]  ? _raw_spin_unlock_irq+0x29/0x40
    [  261.320995]  ? _raw_spin_unlock_irq+0x29/0x40
    [  261.326142]  ? cyc2ns_read_end+0x10/0x10
    [  261.330139]  ? raw_bind+0x280/0x280
    [  261.334138]  ? sched_clock_cpu+0x126/0x170
    [  261.338995]  ? check_flags.part.36+0x450/0x450
    [  261.342991]  ? __lock_acquire+0x4500/0x4500
    [  261.348994]  ? inet_sendmsg+0x11c/0x500
    [  261.352989]  ? dst_output+0x180/0x180
    [  261.357012]  inet_sendmsg+0x11c/0x500
    [ ... ]
    
    v2:
     - clear skb->sk at reassembly routine.(Eric Dumarzet)
    
    Fixes: fa0f5273 ("ip: use rb trees for IP frag queue.")
    Suggested-by: default avatarEric Dumazet <edumazet@google.com>
    Signed-off-by: default avatarTaehee Yoo <ap420073@gmail.com>
    Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    5d407b07
ip_fragment.c 24.1 KB