From: Deepanshu Kartikey Date: Mon, 9 Mar 2026 10:48:59 +0000 (+0530) Subject: comedi: dt2815: add hardware detection to prevent crash X-Git-Tag: v7.0-rc7~8^2~9 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=93853512f565e625df2397f0d8050d6aafd7c3ad;p=thirdparty%2Fkernel%2Flinux.git comedi: dt2815: add hardware detection to prevent crash 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 Closes: https://syzkaller.appspot.com/bug?extid=72f94b474d6e50b71ffc Tested-by: syzbot+72f94b474d6e50b71ffc@syzkaller.appspotmail.com Reviewed-by: Ian Abbott Signed-off-by: Deepanshu Kartikey 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 --- diff --git a/drivers/comedi/drivers/dt2815.c b/drivers/comedi/drivers/dt2815.c index 03ba2fd18a21..d066dc303520 100644 --- a/drivers/comedi/drivers/dt2815.c +++ b/drivers/comedi/drivers/dt2815.c @@ -175,6 +175,18 @@ static int dt2815_attach(struct comedi_device *dev, struct comedi_devconfig *it) ? current_range_type : voltage_range_type; } + /* + * Check if hardware is present before attempting any I/O operations. + * Reading 0xff from status register typically indicates no hardware + * on the bus (floating bus reads as all 1s). + */ + if (inb(dev->iobase + DT2815_STATUS) == 0xff) { + dev_err(dev->class_dev, + "No hardware detected at I/O base 0x%lx\n", + dev->iobase); + return -ENODEV; + } + /* Init the 2815 */ outb(0x00, dev->iobase + DT2815_STATUS); for (i = 0; i < 100; i++) {