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SubjectRe: BUG: please report to => prev = 0, last = 0 at net/dccp/ccids/lib/packet_history.c:LINE/tfrc_rx_his
On Wed, May 09, 2018 at 07:23:41AM +0200, 'Dmitry Vyukov' via syzkaller-bugs wrote:
> On Wed, May 9, 2018 at 7:05 AM, Eric Biggers <ebiggers3@gmail.com> wrote:
> > On Sat, May 05, 2018 at 05:57:02PM -0700, syzbot wrote:
> >> 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: syzbot+99858724c0ba555a12ea@syzkaller.appspotmail.com
> >>
> >> 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 dccp@vger.kernel.org => 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
> >>
> >>
> >> ---
> >> This bug is generated by a bot. It may contain errors.
> >> See https://goo.gl/tpsmEJ for more information about syzbot.
> >> syzbot engineers can be reached at syzkaller@googlegroups.com.
> >>
> >> syzbot will keep track of this bug report.
> >> If you forgot to add the Reported-by tag, once the fix for this bug is
> >> merged
> >> into any tree, please reply to this email with:
> >> #syz fix: exact-commit-title
> >> If you want to test a patch for this bug, please reply with:
> >> #syz test: git://repo/address.git branch
> >> and provide the patch inline or as an attachment.
> >> To mark this as a duplicate of another syzbot report, please reply with:
> >> #syz dup: exact-subject-of-another-report
> >
> > There's already a bug report with this title, this one just had a few characters
> > truncated from the end. Dmitry, is that intentional? The other one is
> > https://groups.google.com/forum/#!msg/syzkaller-bugs/u5nq3PdPkIc/bBFjKHXPAgAJ:
> >
> > #syz dup: BUG: please report to dc...@vger.kernel.org => prev = 0, last = 0 at net/dccp/ccids/lib/packet_history.c:LINE/tfrc_rx_hist_sample_rtt()
>
> I think this happened when we started truncating kernel crash titles
> to 120 columns, so it's intentional.
> However, the dup command did not pass. It's hard to understand who
> received what today, but this suggests that somebody altered email in
> the command to dc...@vger.kernel.org:
> https://groups.google.com/forum/message/raw?msg=syzkaller-bugs/GMndq4-h7BI/VIz4aBEOAwAJ
> We can also mark the old one as invalid.
>

Ah, that was my fault -- I must have copied the bug title from the
syzkaller-bugs Google Groups page, which had mangled the email address in the
bug title. The actual title was:

#syz dup: BUG: please report to dccp@vger.kernel.org => prev = 0, last = 0 at net/dccp/ccids/lib/packet_history.c:LINE/tfrc_rx_hist_sample_rtt()

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