Hi, On 1/10/22 08:16, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 82192cb497f9 Merge branch 'ena-capabilities-field-and-cosm.. > git tree: net-next > console output: https://syzkaller.appspot.com/x/log.txt?x=12ec95c7b00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=322a0a6462d9ff7d > dashboard link: https://syzkaller.appspot.com/bug?extid=94641ba6c1d768b1e35e > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=100ea4e3b00000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13977b73b00000 > > Bisection is inconclusive: the issue happens on the oldest tested release. Regarding commit 793734b587a6: Author: Gerrit Renker <gerrit@xxxxxxxxxxxxxx> Date: Mon Feb 27 12:29:44 2012 -0700 dccp ccid-3: replace incorrect BUG_ON Is this an algorithm (RFC) problem or a Linux implementation problem? Could we round a calculated 0 (unbounded) t_ipi up to 1? Or is just something "nasty" that the reproducer program is doing? I ran the C reproducer for about 15 seconds and got 71 occurrences of this DCCP_BUG_ON(hc->tx_t_ipi == 0); > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13698c63b00000 > final oops: https://syzkaller.appspot.com/x/report.txt?x=10e98c63b00000 > console output: https://syzkaller.appspot.com/x/log.txt?x=17698c63b00000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+94641ba6c1d768b1e35e@xxxxxxxxxxxxxxxxxxxxxxxxx > > BUG: "hc->tx_t_ipi == 0" holds (exception!) at net/dccp/ccids/ccid3.c:90/ccid3_update_send_interval() > CPU: 0 PID: 29976 Comm: syz-executor890 Not tainted 5.16.0-rc8-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 > ccid3_update_send_interval net/dccp/ccids/ccid3.c:90 [inline] > ccid3_update_send_interval.cold+0x87/0x93 net/dccp/ccids/ccid3.c:86 > ccid3_hc_tx_update_s net/dccp/ccids/ccid3.c:169 [inline] > ccid3_hc_tx_packet_sent+0x12e/0x160 net/dccp/ccids/ccid3.c:353 > ccid_hc_tx_packet_sent net/dccp/ccid.h:175 [inline] > dccp_xmit_packet+0x2f2/0x750 net/dccp/output.c:289 > dccp_write_xmit+0x16d/0x1d0 net/dccp/output.c:366 > dccp_sendmsg+0x922/0xc90 net/dccp/proto.c:783 > inet_sendmsg+0x99/0xe0 net/ipv4/af_inet.c:819 > sock_sendmsg_nosec net/socket.c:705 [inline] > sock_sendmsg+0xcf/0x120 net/socket.c:725 > ____sys_sendmsg+0x331/0x810 net/socket.c:2413 > ___sys_sendmsg+0xf3/0x170 net/socket.c:2467 > __sys_sendmmsg+0x195/0x470 net/socket.c:2553 > __do_sys_sendmmsg net/socket.c:2582 [inline] > __se_sys_sendmmsg net/socket.c:2579 [inline] > __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2579 > 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: 0033:0x7f2cf5f36da9 > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 15 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007f2cf5ee4308 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 > RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f2cf5f36da9 > RDX: 0000000000000001 RSI: 000000002000bf40 RDI: 0000000000000004 > RBP: 00007f2cf5fbf4c8 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f2cf5fbf4c0 > R13: 00007f2cf5f8c5dc R14: 00007f2cf5ee4400 R15: 0000000000022000 > </TASK> > > > --- > This report 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@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > For information about bisection process see: https://goo.gl/tpsmEJ#bisection > syzbot can test patches for this issue, for details see: > https://goo.gl/tpsmEJ#testing-patches thanks. -- ~Randy
