Subject: BUG: please report to [email-masked] => prev = 0, last = 0 at net/dccp/ccids/lib/packet_history.c:LINE/tfrc_rx_his

From: syzbot <[email-masked]>
Date: Sat, 05 May 2018 17:57:02 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    c1c07416cdd4 Merge tag 'kbuild-fixes-v4.17' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13d5de47800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5a1dc06635c10d27
dashboard link: https://syzkaller.appspot.com/bug?extid=99858724c0ba555a12ea
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=170afde7800000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=141b4be7800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
BUG: please report to [email-masked] => prev = 0, last = 0 at  
net/dccp/ccids/lib/packet_history.c:425/tfrc_rx_hist_sample_rtt()
CPU: 0 PID: 4495 Comm: syz-executor551 Not tainted 4.17.0-rc3+ #34
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
  tfrc_rx_hist_sample_rtt.cold.3+0x54/0x5c  
net/dccp/ccids/lib/packet_history.c:422
  ccid3_hc_rx_packet_recv+0x5c8/0xed0 net/dccp/ccids/ccid3.c:765
  ccid_hc_rx_packet_recv net/dccp/ccid.h:185 [inline]
  dccp_deliver_input_to_ccids+0xf0/0x280 net/dccp/input.c:180
  dccp_rcv_established+0x87/0xb0 net/dccp/input.c:378
  dccp_v4_do_rcv+0x153/0x180 net/dccp/ipv4.c:654
  sk_backlog_rcv include/net/sock.h:909 [inline]
  __sk_receive_skb+0x3a2/0xd60 net/core/sock.c:513
  dccp_v4_rcv+0x10e5/0x1f3f net/dccp/ipv4.c:875
  ip_local_deliver_finish+0x2e3/0xd80 net/ipv4/ip_input.c:215
  NF_HOOK include/linux/netfilter.h:288 [inline]
  ip_local_deliver+0x1e1/0x720 net/ipv4/ip_input.c:256
  dst_input include/net/dst.h:450 [inline]
  ip_rcv_finish+0x81b/0x2200 net/ipv4/ip_input.c:396
  NF_HOOK include/linux/netfilter.h:288 [inline]
  ip_rcv+0xb70/0x143d net/ipv4/ip_input.c:492
  __netif_receive_skb_core+0x26f5/0x3630 net/core/dev.c:4592
  __netif_receive_skb+0x2c/0x1e0 net/core/dev.c:4657
  process_backlog+0x219/0x760 net/core/dev.c:5337
  napi_poll net/core/dev.c:5735 [inline]
  net_rx_action+0x7b7/0x1930 net/core/dev.c:5801
  __do_softirq+0x2e0/0xaf5 kernel/softirq.c:285
  do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1046
  </IRQ>
  do_softirq.part.17+0x14d/0x190 kernel/softirq.c:329
  do_softirq arch/x86/include/asm/preempt.h:23 [inline]
  __local_bh_enable_ip+0x1ec/0x230 kernel/softirq.c:182
  local_bh_enable include/linux/bottom_half.h:32 [inline]
  rcu_read_unlock_bh include/linux/rcupdate.h:728 [inline]
  ip_finish_output2+0xab2/0x1840 net/ipv4/ip_output.c:231
  ip_finish_output+0x828/0xf80 net/ipv4/ip_output.c:317
  NF_HOOK_COND include/linux/netfilter.h:277 [inline]
  ip_output+0x21b/0x850 net/ipv4/ip_output.c:405
  dst_output include/net/dst.h:444 [inline]
  ip_local_out+0xc5/0x1b0 net/ipv4/ip_output.c:124
  ip_queue_xmit+0x9d7/0x1f70 net/ipv4/ip_output.c:504
  dccp_transmit_skb+0x999/0x12e0 net/dccp/output.c:142
  dccp_xmit_packet+0x250/0x790 net/dccp/output.c:281
  dccp_write_xmit+0x190/0x1f0 net/dccp/output.c:363
  dccp_sendmsg+0x8c7/0x1020 net/dccp/proto.c:818
  inet_sendmsg+0x19f/0x690 net/ipv4/af_inet.c:798
  sock_sendmsg_nosec net/socket.c:629 [inline]
  sock_sendmsg+0xd5/0x120 net/socket.c:639
  ___sys_sendmsg+0x525/0x940 net/socket.c:2117
  __sys_sendmmsg+0x240/0x6f0 net/socket.c:2212
  __do_sys_sendmmsg net/socket.c:2241 [inline]
  __se_sys_sendmmsg net/socket.c:2238 [inline]
  __x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2238
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445d09
RSP: 002b:00007f3c7eff5d88 EFLAGS: 00000293 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00000000006dac40 RCX: 0000000000445d09
RDX: 0000000000000001 RSI: 000000

---
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