linux-kernel - [Linux kernel bug] UBSAN: shift-out-of-bounds in dctcp_update

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Date: Fri, 17 May 2024 13:03:18 +0800
From: Sam Sun <samsun1006219@...il.com>
To: linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Cc: Eric Dumazet <edumazet@...gle.com>, kuba@...nel.org, davem@...emloft.net, 
	dsahern@...nel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com, 
	xrivendell7@...il.com
Subject: [Linux kernel bug] UBSAN: shift-out-of-bounds in dctcp_update_alpha

Dear developers and maintainers,

We encountered a shift-out-of-bounds bug while using our modified
syzkaller. It was tested against the latest upstream kernel (6.9). The
kernel was compiled by clang 14.0.0, and kernel config and C repro are
attached to this email. Kernel crash log is listed below.
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in net/ipv4/tcp_dctcp.c:143:12
shift exponent 100 is too large for 32-bit type 'u32' (aka 'unsigned int')
CPU: 0 PID: 8083 Comm: syz-executor345 Not tainted 6.9.0-05151-g1b294a1f3561 #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x201/0x300 lib/dump_stack.c:114
 ubsan_epilogue lib/ubsan.c:231 [inline]
 __ubsan_handle_shift_out_of_bounds+0x346/0x3a0 lib/ubsan.c:468
 dctcp_update_alpha+0x540/0x570 net/ipv4/tcp_dctcp.c:143
 tcp_in_ack_event net/ipv4/tcp_input.c:3802 [inline]
 tcp_ack+0x17b1/0x3bc0 net/ipv4/tcp_input.c:3948
 tcp_rcv_state_process+0x57a/0x2290 net/ipv4/tcp_input.c:6711
 tcp_v4_do_rcv+0x764/0xc40 net/ipv4/tcp_ipv4.c:1937
 sk_backlog_rcv include/net/sock.h:1106 [inline]
 __release_sock+0x20f/0x350 net/core/sock.c:2983
 release_sock+0x61/0x1f0 net/core/sock.c:3549
 mptcp_subflow_shutdown+0x3d0/0x620 net/mptcp/protocol.c:2907
 mptcp_check_send_data_fin+0x225/0x410 net/mptcp/protocol.c:2976
 __mptcp_close+0x238/0xad0 net/mptcp/protocol.c:3072
 mptcp_close+0x2a/0x1a0 net/mptcp/protocol.c:3127
 inet_release+0x190/0x1f0 net/ipv4/af_inet.c:437
 __sock_release net/socket.c:659 [inline]
 sock_close+0xc0/0x240 net/socket.c:1421
 __fput+0x41b/0x890 fs/file_table.c:422
 task_work_run+0x23b/0x300 kernel/task_work.c:180
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0x9c8/0x2540 kernel/exit.c:878
 do_group_exit+0x201/0x2b0 kernel/exit.c:1027
 __do_sys_exit_group kernel/exit.c:1038 [inline]
 __se_sys_exit_group kernel/exit.c:1036 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xe4/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x67/0x6f
RIP: 0033:0x7f6c2b5005b6
Code: Unable to access opcode bytes at 0x7f6c2b50058c.
RSP: 002b:00007ffe883eb948 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007f6c2b5862f0 RCX: 00007f6c2b5005b6
RDX: 0000000000000001 RSI: 000000000000003c RDI: 0000000000000001
RBP: 0000000000000001 R08: 00000000000000e7 R09: ffffffffffffffc0
R10: 0000000000000006 R11: 0000000000000246 R12: 00007f6c2b5862f0
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001
 </TASK>
---[ end trace ]---
If you have any questions, please contact us.

Reported by Yue Sun <samsun1006219@...il.com>
Reported by xingwei lee <xrivendell7@...il.com>

Best Regards,
Yue

Download attachment "config" of type "application/octet-stream" (248322 bytes)

View attachment "dctcp_update_alpha.c" of type "text/x-csrc" (39424 bytes)