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PacktPublishing / Linux-Kernel-Programming

Linux Kernel Programming, published by Packt
MIT License
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The "lkm" script fails on dmesg permissions #1

Closed gregbuchholz closed 3 years ago

gregbuchholz commented 3 years ago

Changing to "sudo dmesg" fixes it.

gregbuchholz commented 3 years ago

This was with Ubuntu 21.04

gregbuchholz commented 3 years ago

I had compiled a new 5.13.11 based on localmodconfig in a virtual machine. Searching the .config file does confirm that CONFIG_SECURITY_DMESG_RESTRICT is set to 'y'. Then booting the stock 5.11.0-31-generic kernel that came with the Ubuntu 21.04 install, I get the same behavior with dmesg needing root permissions. This is also consistent with the Lubuntu installed on my laptop. It looks like this might have been a change in Ubuntu starting with the 20.10 release. See also:

"Ubuntu 20.10 Moving Ahead In Restricting Access To dmesg"

https://www.phoronix.com/scan.php?page=news_item&px=Ubuntu-20.10-dmesg-Needs-Root

kaiwan commented 3 years ago

I had compiled a new 5.13.11 based on localmodconfig in a virtual machine. Searching the .config file does confirm that >CONFIG_SECURITY_DMESG_RESTRICT is set to 'y'. Right; this makes sense..

"Ubuntu 20.10 Moving Ahead In Restricting Access To dmesg" https://www.phoronix.com/scan.php?page=news_item&px=Ubuntu-20.10-dmesg-Needs-Root Ah, then no wonder... the book uses Ubuntu 20.04, so didn't require sudo. Ok, lets enable it now, as in any case, sudo is used within the script (so, the default sudo timeout should ensure that the password is in any case requested only once). Thank you!