insmod error in kernel module programming

Question

I am just starting with modular programming.

Above are my two files:

hello.c

#include <linux/init.h>
#include <linux/module.h>

static int hello_init(void)
{
    printk(KERN_ALERT "TEST: Hello world\n");
    return 0;
}

static void hello_exit(void)
{
    printk(KERN_ALERT "TEST: Good Bye");
}

module_init(hello_init);
module_exit(hello_exit);

Makefile

obj-m += hello.o

KDIR = /usr/src/linux-headers-3.13.0-46-generic

all:
    $(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules

clean:
    rm -rf *.o *.ko *.mod.* *.symvers *.order

And here's my terminal output showing error in insmod command, kindly help.

anubhav@anubhav-Inspiron-3421:~/Desktop/os$ make
make -C /usr/src/linux-headers-3.13.0-46-generic  SUBDIRS=/home/anubhav/Desktop/os modules
make[1]: Entering directory `/usr/src/linux-headers-3.13.0-46-generic'
Building modules, stage 2.
MODPOST 1 modules
make[1]: Leaving directory `/usr/src/linux-headers-3.13.0-46-generic'
anubhav@anubhav-Inspiron-3421:~/Desktop/os$ insmod hello.ko
insmod: ERROR: could not insert module hello.ko: Operation not permitted

Only the root user typically has permissions to insert/remove kernel modules. Either su to root, or use sudo (if applicable) to run the command as root. — lsowen
– lsowen, Commented Mar 13, 2015 at 16:12
@lsowen I tried "su" and "su -". But after providing password, i get the msg "su: Authentication failure". Any other way to move ahead — anubhav
– anubhav, Commented Mar 13, 2015 at 16:17
This message means you put in the wrong password (or are not a member of a user group allowed to become root). The password you need to use at su is the root password, not your user password. — lsowen
– lsowen, Commented Mar 13, 2015 at 16:19
@lsowen ubuntu website says that user can prepend any command that needs to be executed as root with sudo command. My insmod command worked and i got the message using dmesg. Thanks. — anubhav
– anubhav, Commented Mar 13, 2015 at 16:25
And you dont see printk(KERN_ALERT "TEST: Good Bye"); because you have not done rmmod hello have you? — Milind Dumbare
– Milind Dumbare, Commented Mar 13, 2015 at 17:00

Abhishek Jaisingh · Accepted Answer · 2019-05-30 19:50:13Z

3

If you have secure boot enabled, the newer kernels won't allow inserting arbitrary kernel modules. So, either you can disable secure boot in your BIOS or you need to sign the kernel modules you want to install.

Steps to securely sign your kernel modules:

Create a X509 certificate that can be imported in firmware
Enrolling the public key just created
Sign the module you want to install
Install the module

You need to be root to do steps 2 & 4. The detailed process is described in a nice Ubuntu blog.

answered May 30, 2019 at 19:50

Abhishek Jaisingh

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Milind Dumbare · Accepted Answer · 2015-03-13 17:13:01Z

1

As isowen mentioned only root can load or unload the module.

You see the print in hello_init() when you do insmod hello and you see the print in hello_exit() when you do rmmod hello.

answered Mar 13, 2015 at 17:13

Milind Dumbare

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nu11secur1ty · Accepted Answer · 2019-10-08 12:14:05Z

0

execute cat /proc/sys/kernel/modules_disabled and if you see the result 1 then execute echo 'kernel.modules_disabled=1' >> /etc/sysctl.d/99-custom.conf then reboot and try again. ;) BR nu11secur1ty

answered Oct 8, 2019 at 12:14

nu11secur1ty

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