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e9e14a558f8ab-435dd070263mr43345405ab.12.1764160383391; Wed, 26 Nov 2025 04:33:03 -0800 (PST) Date: Wed, 26 Nov 2025 04:33:03 -0800 In-Reply-To: <5e24b887-4eb3-474e-9560-fd0c0ffacb8e@kernel.org> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6926f37f.a70a0220.d98e3.00d5.GAE@google.com> Subject: Re: [syzbot] [net?] divide error in __tcp_select_window (4) From: syzbot To: linux-kernel@vger.kernel.org, matttbe@kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: divide error in __tcp_select_window 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fbc0bc37038 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007fbc0afe5fa0 RCX: 00007fbc0ad8f749 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00007fbc0bc37090 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00007fbc0afe6038 R14: 00007fbc0afe5fa0 R15: 00007ffe094ab938 Oops: divide error: 0000 [#1] SMP KASAN PTI CPU: 0 UID: 0 PID: 6503 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 RIP: 0010:__tcp_select_window+0x7a2/0x1270 net/ipv4/tcp_output.c:3333 Code: ff ff ff 44 89 e1 d3 e0 89 c1 f7 d1 41 01 ce 41 21 c6 e9 c5 00 00 00 e8 8c c6 01 f8 e9 b8 00 00 00 e8 82 c6 01 f8 44 89 f0 99 7c 24 2c 41 29 d6 48 bb 00 00 00 00 00 fc ff df e9 9c 00 00 00 RSP: 0018:ffffc90002e67640 EFLAGS: 00010293 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88802e693c80 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffffc90002e67730 R08: ffff888027d78143 R09: 1ffff11004faf028 R10: dffffc0000000000 R11: ffffed1004faf029 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: ffff88802fdc24f0 FS: 00007fbc0bc376c0(0000) GS:ffff888126139000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00005587d939f950 CR3: 000000007c31a000 CR4: 00000000003526f0 Call Trace: tcp_select_window net/ipv4/tcp_output.c:280 [inline] __tcp_transmit_skb+0xbc7/0x3aa0 net/ipv4/tcp_output.c:1565 tcp_transmit_skb net/ipv4/tcp_output.c:1646 [inline] tcp_send_active_reset+0x2d1/0x5b0 net/ipv4/tcp_output.c:3828 mptcp_do_fastclose+0x27e/0x380 net/mptcp/protocol.c:2801 mptcp_disconnect+0x238/0x710 net/mptcp/protocol.c:3261 mptcp_sendmsg_fastopen+0x2f8/0x580 net/mptcp/protocol.c:1775 mptcp_sendmsg+0x1774/0x1980 net/mptcp/protocol.c:1854 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg+0xe5/0x270 net/socket.c:742 __sys_sendto+0x3bd/0x520 net/socket.c:2244 __do_sys_sendto net/socket.c:2251 [inline] __se_sys_sendto net/socket.c:2247 [inline] __x64_sys_sendto+0xde/0x100 net/socket.c:2247 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fbc0ad8f749 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fbc0bc37038 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007fbc0afe5fa0 RCX: 00007fbc0ad8f749 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00007fbc0bc37090 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00007fbc0afe6038 R14: 00007fbc0afe5fa0 R15: 00007ffe094ab938 Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:__tcp_select_window+0x7a2/0x1270 net/ipv4/tcp_output.c:3333 Code: ff ff ff 44 89 e1 d3 e0 89 c1 f7 d1 41 01 ce 41 21 c6 e9 c5 00 00 00 e8 8c c6 01 f8 e9 b8 00 00 00 e8 82 c6 01 f8 44 89 f0 99 7c 24 2c 41 29 d6 48 bb 00 00 00 00 00 fc ff df e9 9c 00 00 00 RSP: 0018:ffffc90002e67640 EFLAGS: 00010293 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88802e693c80 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffffc90002e67730 R08: ffff888027d78143 R09: 1ffff11004faf028 R10: dffffc0000000000 R11: ffffed1004faf029 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: ffff88802fdc24f0 FS: 00007fbc0bc376c0(0000) GS:ffff888126139000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00005587d939f950 CR3: 000000007c31a000 CR4: 00000000003526f0 ---------------- Code disassembly (best guess), 1 bytes skipped: 0: ff c3 inc %ebx 2: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1) 9: 00 00 00 c: 0f 1f 40 00 nopl 0x0(%rax) 10: 48 89 f8 mov %rdi,%rax 13: 48 89 f7 mov %rsi,%rdi 16: 48 89 d6 mov %rdx,%rsi 19: 48 89 ca mov %rcx,%rdx 1c: 4d 89 c2 mov %r8,%r10 1f: 4d 89 c8 mov %r9,%r8 22: 4c 8b 4c 24 08 mov 0x8(%rsp),%r9 27: 0f 05 syscall * 29: 48 3d 01 f0 ff ff cmp $0xfffffffffffff001,%rax <-- trapping instruction 2f: 73 01 jae 0x32 31: c3 ret 32: 48 c7 c1 a8 ff ff ff mov $0xffffffffffffffa8,%rcx 39: f7 d8 neg %eax 3b: 64 89 01 mov %eax,%fs:(%rcx) 3e: 48 rex.W Tested on: commit: b3717b4d DO-NOT-MERGE: mptcp: enabled by default git tree: git://git.kernel.org/pub/scm/linux/kernel/git/matttbe/net-next.git b4/net-mptcp-clear-sched-rtx console output: https://syzkaller.appspot.com/x/log.txt?x=1037ee92580000 kernel config: https://syzkaller.appspot.com/x/.config?x=14b6a9313e132a6b dashboard link: https://syzkaller.appspot.com/bug?extid=3a92d359bc2ec6255a33 compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8 Note: no patches were applied.