I am running a Fedora kernel ver: 4.15.3-300.fc27.i686). I am trying to load a custom device driver. When I try to use the device (via an open() call in a C program) the call errors out with errno equal to 6 (ENODEV). When I look into this further, I see the following messages from dmesg:

[Tue Apr 24 17:34:32 2018] mymodule: loading out-of-tree module taints kernel.
[Tue Apr 24 17:34:32 2018] mymodule: module verification failed: signature and/or required key missing - tainting kernel

I think this is an issue with the driver not being signed. The Fedora System Administrator's Guide tells me that I need to rebuild the kernel to add a new key, but is also says that

If UEFI Secure Boot is disabled and if the module.sig_enforce kernel parameter has not been specified, then unsigned kernel modules and signed kernel modules without a public key can be successfully loaded.

The computer I am running uses BIOS and does not support UEFI.

How do I find out what the current value of the module.sig_enforce setting is, and how do I change it?

  • Check your kernel command line. Usually in your grub configuration. If you didn't specify it when you booted the system, then it's not set. – Michael Hampton Apr 25 '18 at 23:14
  • What would the syntax for that look like? This is the line from grub.cfg: linux16 /vmlinuz-4.17.0-0.rc2.git0.1.vanilla.knurd.1.fc27.i686 root=/dev /mapper/fedora-root ro rd.md.uuid=e8f1fe90:c8761aac:48d12b1a:7f3251b5 rd.lvm.lv= fedora/root rd.md.uuid=7e8e6e41:46f1b47f:1b65099f:a33152a8 rd.lvm.lv=fedora/swap rhgb quiet LANG=en_US.UTF-8 initrd16 /initramfs-4.17.0-0.rc2.git0.1.vanilla.knurd.1.fc27.i686.img – Jay Elston Apr 26 '18 at 23:04
  • I don't see module.sig_enforce anywhere in there. So you aren't using it. – Michael Hampton Apr 26 '18 at 23:15
  • Ahh - also found this in /usr/lib/modules/4.15.3-300.fc27.i686/config: #CONFIG_MODULE_SIG_FORCE is not set; however CONFIG_MODULE_SIG=y so I need to turn that off as well. – Jay Elston Apr 26 '18 at 23:33

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