bisecting fixing commit since 1434a3127887a7e708be5f4edd5e36d64d8622f8 building syzkaller on 3c7fef3361a6007112b26adc1c5a550189ef43fe testing commit 1434a3127887a7e708be5f4edd5e36d64d8622f8 compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1 kernel signature: 748a4c57c669c749792d994c76ea186d1f0c9fb3522a12d2adf7f199d32fffba all runs: crashed: divide error in tcp_reno_cong_avoid testing current HEAD f0fddcec6b6254b4b3611388786bbafb703ad257 testing commit f0fddcec6b6254b4b3611388786bbafb703ad257 compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.1 kernel signature: 35bbf64c96fac4f6787a661cb4e7cde3cf550c16c12557d476d1d7d17b70c255 all runs: crashed: divide error in tcp_reno_cong_avoid revisions tested: 2, total time: 21m25.756077178s (build: 13m32.719043027s, test: 7m9.746879808s) the crash still happens on HEAD commit msg: Merge tag 'for-5.14-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux crash: divide error in tcp_reno_cong_avoid nf_conntrack: default automatic helper assignment has been turned off for security reasons and CT-based firewall rule not found. Use the iptables CT target to attach helpers instead. divide error: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 10214 Comm: syz-executor.1 Not tainted 5.14.0-rc2-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:tcp_cong_avoid_ai net/ipv4/tcp_cong.c:420 [inline] RIP: 0010:tcp_reno_cong_avoid+0x1fd/0x2b0 net/ipv4/tcp_cong.c:450 Code: ab 48 09 00 00 44 89 e5 45 39 ec 41 0f 47 ed 85 c0 89 ab 40 09 00 00 0f 85 01 ff ff ff 48 83 c4 08 5b 5d 41 5c 41 5d c3 31 d2 f5 01 c1 89 93 44 09 00 00 89 8b 40 09 00 00 e9 30 ff ff ff c7 RSP: 0018:ffffc9000b5c76b0 EFLAGS: 00010246 RAX: 0000000000000011 RBX: ffff88802c398bc0 RCX: 0000000000000001 RDX: 0000000000000000 RSI: 000000007bf6661b RDI: ffff88802c399504 RBP: 0000000000000000 R08: dffffc0000000000 R09: 0000000078c8a2f1 R10: 00000000ca697579 R11: ffff88802c3993b0 R12: 0000000000000000 R13: 00000000ffffffff R14: 0000000000000011 R15: ffff88802c399500 FS: 00007f4192cd4700(0000) GS:ffff8880b9e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000005680c0 CR3: 000000002c2f3000 CR4: 00000000001506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: tcp_cdg_cong_avoid+0x47d/0x1410 net/ipv4/tcp_cdg.c:293 tcp_cong_avoid net/ipv4/tcp_input.c:3091 [inline] tcp_cong_control net/ipv4/tcp_input.c:3449 [inline] tcp_ack+0x312f/0x56b0 net/ipv4/tcp_input.c:3850 tcp_rcv_established+0x4e0/0x2100 net/ipv4/tcp_input.c:5887 tcp_v4_do_rcv+0x4f4/0x760 net/ipv4/tcp_ipv4.c:1694 sk_backlog_rcv include/net/sock.h:1023 [inline] __release_sock+0x113/0x360 net/core/sock.c:2655 __sk_flush_backlog+0x1d/0x30 net/core/sock.c:2675 sk_flush_backlog include/net/sock.h:1110 [inline] tcp_sendmsg_locked+0x223e/0x2e40 net/ipv4/tcp.c:1305 tcp_sendmsg+0x23/0x40 net/ipv4/tcp.c:1461 sock_sendmsg_nosec net/socket.c:703 [inline] sock_sendmsg+0xab/0xe0 net/socket.c:723 __sys_sendto+0x1a4/0x270 net/socket.c:2019 __do_sys_sendto net/socket.c:2031 [inline] __se_sys_sendto net/socket.c:2027 [inline] __x64_sys_sendto+0xd8/0x1b0 net/socket.c:2027 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: 0033:0x4665d9 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:00007f4192cd4188 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665d9 RDX: 00000000fffffd46 RSI: 0000000020000240 RDI: 0000000000000004 RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 00000000000001f4 R10: 00000000000081f4 R11: 0000000000000246 R12: 000000000056bf80 R13: 00007fff615280cf R14: 00007f4192cd4300 R15: 0000000000022000 Modules linked in: ---[ end trace a5c6657a635e497a ]--- RIP: 0010:tcp_cong_avoid_ai net/ipv4/tcp_cong.c:420 [inline] RIP: 0010:tcp_reno_cong_avoid+0x1fd/0x2b0 net/ipv4/tcp_cong.c:450 Code: ab 48 09 00 00 44 89 e5 45 39 ec 41 0f 47 ed 85 c0 89 ab 40 09 00 00 0f 85 01 ff ff ff 48 83 c4 08 5b 5d 41 5c 41 5d c3 31 d2 f5 01 c1 89 93 44 09 00 00 89 8b 40 09 00 00 e9 30 ff ff ff c7 RSP: 0018:ffffc9000b5c76b0 EFLAGS: 00010246 RAX: 0000000000000011 RBX: ffff88802c398bc0 RCX: 0000000000000001 RDX: 0000000000000000 RSI: 000000007bf6661b RDI: ffff88802c399504 RBP: 0000000000000000 R08: dffffc0000000000 R09: 0000000078c8a2f1 R10: 00000000ca697579 R11: ffff88802c3993b0 R12: 0000000000000000 R13: 00000000ffffffff R14: 0000000000000011 R15: ffff88802c399500 FS: 00007f4192cd4700(0000) GS:ffff8880b9e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fb1a803d0b8 CR3: 000000002c2f3000 CR4: 00000000001506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400