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BUG: KCSAN: data-race in mISDN_ioctl / mISDN_read

write to 0xffff888109eca460 of 4 bytes by task 23833 on cpu 0:
 misdn_add_timer drivers/isdn/mISDN/timerdev.c:175 [inline]
 mISDN_ioctl+0x2fb/0x550 drivers/isdn/mISDN/timerdev.c:233
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:892
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:892
 x64_sys_call+0x19a8/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888109eca460 of 4 bytes by task 23829 on cpu 1:
 mISDN_read+0x1b4/0x470 drivers/isdn/mISDN/timerdev.c:112
 do_loop_readv_writev include/linux/uio.h:-1 [inline]
 vfs_readv+0x3e6/0x670 fs/read_write.c:1018
 do_readv+0xe7/0x210 fs/read_write.c:1078
 __do_sys_readv fs/read_write.c:1163 [inline]
 __se_sys_readv fs/read_write.c:1160 [inline]
 __x64_sys_readv+0x45/0x50 fs/read_write.c:1160
 x64_sys_call+0x29af/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:20
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 23829 Comm: +}[@ Not tainted 6.15.0-rc3-syzkaller-00342-g5bc1018675ec #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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