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

From: syzbot <[email-masked]>
Date: Thu, 26 Aug 2021 09:29:24 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    e3f30ab28ac8 Merge branch 'pktgen-samples-next'
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13a18a59300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ef482942966bf763
dashboard link: https://syzkaller.appspot.com/bug?extid=d9bd66f8d352f7eb1955
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12bfe5d5300000

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

BUG: please report to [email-masked] => prev = 0, last = 0 at net/dccp/ccids/lib/packet_history.c:414/tfrc_rx_hist_sample_rtt()
CPU: 1 PID: 13730 Comm: syz-executor.2 Not tainted 5.14.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
 tfrc_rx_hist_sample_rtt+0x4a5/0x4b0 net/dccp/ccids/lib/packet_history.c:414
 ccid3_hc_rx_packet_recv+0x5b8/0xe90 net/dccp/ccids/ccid3.c:760
 ccid_hc_rx_packet_recv net/dccp/ccid.h:182 [inline]
 dccp_deliver_input_to_ccids+0xd9/0x250 net/dccp/input.c:176
 dccp_rcv_established net/dccp/input.c:374 [inline]
 dccp_rcv_established+0x107/0x160 net/dccp/input.c:364
 dccp_v4_do_rcv+0x130/0x190 net/dccp/ipv4.c:667
 sk_backlog_rcv include/net/sock.h:1024 [inline]
 __release_sock+0x134/0x3b0 net/core/sock.c:2669
 release_sock+0x54/0x1b0 net/core/sock.c:3201
 dccp_sendmsg+0x67a/0xc90 net/dccp/proto.c:796
 inet_sendmsg+0x99/0xe0 net/ipv4/af_inet.c:821
 sock_sendmsg_nosec net/socket.c:704 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:724
 ____sys_sendmsg+0x331/0x810 net/socket.c:2403
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2457
 __sys_sendmmsg+0x195/0x470 net/socket.c:2543
 __do_sys_sendmmsg net/socket.c:2572 [inline]
 __se_sys_sendmmsg net/socket.c:2569 [inline]
 __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2569
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4665e9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f94cb63e188 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 000000000056c0f0 RCX: 00000000004665e9
RDX: 0000000000000002 RSI: 0000000020000240 RDI: 0000000000000004
RBP: 00000000004bfcc4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c0f0
R13: 00007ffd68749c0f R14: 00007f94cb63e300 R15: 0000000000022000

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