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93853512f5
The dt2815 driver crashes when attached to I/O ports without actual hardware present. This occurs because syzkaller or users can attach the driver to arbitrary I/O addresses via COMEDI_DEVCONFIG ioctl. When no hardware exists at the specified port, inb() operations return 0xff (floating bus), but outb() operations can trigger page faults due to undefined behavior, especially under race conditions: BUG: unable to handle page fault for address: 000000007fffff90 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page RIP: 0010:dt2815_attach+0x6e0/0x1110 Add hardware detection by reading the status register before attempting any write operations. If the read returns 0xff, assume no hardware is present and fail the attach with -ENODEV. This prevents crashes from outb() operations on non-existent hardware. Reported-by: syzbot+72f94b474d6e50b71ffc@syzkaller.appspotmail.com Cc: stable <stable@kernel.org> Closes: https://syzkaller.appspot.com/bug?extid=72f94b474d6e50b71ffc Tested-by: syzbot+72f94b474d6e50b71ffc@syzkaller.appspotmail.com Reviewed-by: Ian Abbott <abbotti@mev.co.uk> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com> Link: [https://lore.kernel.org/all/20260126070458.10974-1-kartikey406@gmail.com/T/] Link: [https://lore.kernel.org/all/20260126070458.10974-1-kartikey406@gmail.com/T/ Link: https://patch.msgid.link/20260309104859.503529-1-kartikey406@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>