bisecting fixing commit since f3438b4c4e692b49b7dc2bab864d20381024be16 building syzkaller on 6c236867ce33c0c16b102e02a08226d7eb9b2046 testing commit f3438b4c4e692b49b7dc2bab864d20381024be16 compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.2 kernel signature: fec59177dc569ef0e46b67a8ccec41f5fed28c54c88468652f6380120fff62c7 all runs: crashed: divide error in tcp_reno_cong_avoid testing current HEAD 4f3d93c6eaff6b84e43b63e0d7a119c5920e1020 testing commit 4f3d93c6eaff6b84e43b63e0d7a119c5920e1020 compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.2 kernel signature: 71d9c798e24c40c2a148b664a657e172c0c5b4369200a2656bc86e854ac9700e all runs: crashed: divide error in tcp_reno_cong_avoid revisions tested: 2, total time: 21m32.990347092s (build: 14m38.410660574s, test: 6m18.81412306s) the crash still happens on HEAD commit msg: Merge tag 'drm-fixes-2021-12-31' of git://anongit.freedesktop.org/drm/drm crash: divide error in tcp_reno_cong_avoid divide error: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 4163 Comm: syz-executor.1 Not tainted 5.16.0-rc7-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 88 09 00 00 44 89 e5 45 39 ec 41 0f 47 ed 85 c0 89 ab 80 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 84 09 00 00 89 8b 80 09 00 00 e9 30 ff ff ff c7 RSP: 0018:ffffc90002d1f6d0 EFLAGS: 00010246 RAX: 0000000000000011 RBX: ffff88801d343c00 RCX: 0000000000000001 RDX: 0000000000000000 RSI: 000000004897f11d RDI: ffff88801d344584 RBP: 0000000000000000 R08: dffffc0000000000 R09: 00000000c15ed8e9 R10: 00000000c7c72303 R11: ffff88801d344430 R12: 0000000000000000 R13: 00000000ffffffff R14: 0000000000000011 R15: ffff88801d344580 FS: 00007f39be4eb700(0000) GS:ffff8880b9e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000014a53ad CR3: 00000000611a2000 CR4: 00000000003506f0 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:3131 [inline] tcp_cong_control net/ipv4/tcp_input.c:3488 [inline] tcp_ack+0x31e4/0x5580 net/ipv4/tcp_input.c:3889 tcp_rcv_established+0x4e2/0x2100 net/ipv4/tcp_input.c:5936 tcp_v4_do_rcv+0x536/0x7d0 net/ipv4/tcp_ipv4.c:1719 sk_backlog_rcv include/net/sock.h:1030 [inline] __release_sock+0x113/0x360 net/core/sock.c:2768 __sk_flush_backlog+0x1d/0x30 net/core/sock.c:2788 sk_flush_backlog include/net/sock.h:1117 [inline] tcp_sendmsg_locked+0x246e/0x3320 net/ipv4/tcp.c:1277 tcp_sendmsg+0x23/0x40 net/ipv4/tcp.c:1440 sock_sendmsg_nosec net/socket.c:704 [inline] sock_sendmsg+0xab/0xe0 net/socket.c:724 __sys_sendto+0x1a4/0x270 net/socket.c:2036 __do_sys_sendto net/socket.c:2048 [inline] __se_sys_sendto net/socket.c:2044 [inline] __x64_sys_sendto+0xd8/0x1b0 net/socket.c:2044 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:00007f39be4eb188 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 000000000056c038 RCX: 00000000004665e9 RDX: 00000000fffffd46 RSI: 0000000020000240 RDI: 0000000000000004 RBP: 00000000004bfcc4 R08: 0000000000000000 R09: 00000000000001f4 R10: 00000000000081f4 R11: 0000000000000246 R12: 000000000056c038 R13: 00007fff5614bb2f R14: 00007f39be4eb300 R15: 0000000000022000 Modules linked in: ---[ end trace 1576f867bbd4577e ]--- 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 88 09 00 00 44 89 e5 45 39 ec 41 0f 47 ed 85 c0 89 ab 80 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 84 09 00 00 89 8b 80 09 00 00 e9 30 ff ff ff c7 RSP: 0018:ffffc90002d1f6d0 EFLAGS: 00010246 RAX: 0000000000000011 RBX: ffff88801d343c00 RCX: 0000000000000001 RDX: 0000000000000000 RSI: 000000004897f11d RDI: ffff88801d344584 RBP: 0000000000000000 R08: dffffc0000000000 R09: 00000000c15ed8e9 R10: 00000000c7c72303 R11: ffff88801d344430 R12: 0000000000000000 R13: 00000000ffffffff R14: 0000000000000011 R15: ffff88801d344580 FS: 00007f39be4eb700(0000) GS:ffff8880b9e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fff7871cc60 CR3: 00000000611a2000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 ---------------- Code disassembly (best guess): 0: ab stos %eax,%es:(%rdi) 1: 88 09 mov %cl,(%rcx) 3: 00 00 add %al,(%rax) 5: 44 89 e5 mov %r12d,%ebp 8: 45 39 ec cmp %r13d,%r12d b: 41 0f 47 ed cmova %r13d,%ebp f: 85 c0 test %eax,%eax 11: 89 ab 80 09 00 00 mov %ebp,0x980(%rbx) 17: 0f 85 01 ff ff ff jne 0xffffff1e 1d: 48 83 c4 08 add $0x8,%rsp 21: 5b pop %rbx 22: 5d pop %rbp 23: 41 5c pop %r12 25: 41 5d pop %r13 27: c3 retq 28: 31 d2 xor %edx,%edx * 2a: f7 f5 div %ebp <-- trapping instruction 2c: 01 c1 add %eax,%ecx 2e: 89 93 84 09 00 00 mov %edx,0x984(%rbx) 34: 89 8b 80 09 00 00 mov %ecx,0x980(%rbx) 3a: e9 30 ff ff ff jmpq 0xffffff6f 3f: c7 .byte 0xc7