[syzbot] [sctp?] KCSAN: data-race in sctp_do_sm / sctp_wait_for_connect (4)

Hello,

syzbot found the following issue on:

HEAD commit:    23b0f90ba871 Merge tag 'sysctl-7.00-rc1' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13427ee6580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=70c3ed59b49365c3
dashboard link: https://syzkaller.appspot.com/bug?extid=5a18a1130eb54693214f
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ae3bcc875a04/disk-23b0f90b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1a4dbd53da8f/vmlinux-23b0f90b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3c3824777f5c/bzImage-23b0f90b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5a18a1130eb54693214f@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in sctp_do_sm / sctp_wait_for_connect

write to 0xffff88815e3ad228 of 4 bytes by task 15371 on cpu 1:
 sctp_cmd_new_state net/sctp/sm_sideeffect.c:878 [inline]
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1342 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1204 [inline]
 sctp_do_sm+0xa19/0x3330 net/sctp/sm_sideeffect.c:1175
 sctp_primitive_SHUTDOWN+0x74/0x90 net/sctp/primitive.c:89
 sctp_close+0x272/0x570 net/sctp/socket.c:1529
 inet_release+0xcd/0xf0 net/ipv4/af_inet.c:437
 __sock_release net/socket.c:662 [inline]
 sock_close+0x6b/0x150 net/socket.c:1455
 __fput+0x29b/0x650 fs/file_table.c:469
 ____fput+0x1c/0x30 fs/file_table.c:497
 task_work_run+0x130/0x1a0 kernel/task_work.c:233
 get_signal+0xe0e/0xf60 kernel/signal.c:2807
 arch_do_signal_or_restart+0x96/0x450 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x6a/0x6f0 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x249/0x370 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88815e3ad228 of 4 bytes by task 15375 on cpu 0:
 sctp_wait_for_connect+0x173/0x390 net/sctp/socket.c:9381
 sctp_sendmsg_to_asoc+0xf34/0xf50 net/sctp/socket.c:1884
 sctp_sendmsg+0x13b9/0x1d60 net/sctp/socket.c:2030
 inet_sendmsg+0xc5/0xd0 net/ipv4/af_inet.c:859
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 __sys_sendto+0x3f4/0x4d0 net/socket.c:2206
 __do_sys_sendto net/socket.c:2213 [inline]
 __se_sys_sendto net/socket.c:2209 [inline]
 __x64_sys_sendto+0x76/0x90 net/socket.c:2209
 x64_sys_call+0x2d35/0x3020 arch/x86/include/generated/asm/syscalls_64.h:45
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 15375 Comm: syz.4.3516 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================


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