Question about /dev/mem and /dev/kmem

[Jim Nelson]

I was looking at some articles about rootkits on monolithic kernels, and had a 
thought.  Would a kernel config option to disable write access to /dev/mem and 
/dev/kmem be a workable idea?

I know it'll kill X (unless you're using the framebuffer X server), but would 
there be any other big problems?  SELinux has a finer-grained control over those 
files, but also involves a bit of administrative and system overhead.

I see this as an option that could be used in routers, web servers, firewalls and 
other systems that have a greater risk of exposure to rootkits.  Granted, it only 
makes sense with a monolithic kernel, but most people nowadays would only use 
monolithic kernels for security reasons.  You could also put a couple of 
printk()'s in to raise alarms if someone does try to open the device file for writing.

Am I speaking ex rectum?  Granted, I'm kinda new to this, but I can't see any 
reason not to offer the choice to someone compiling a kernel - and I think it 
could be done with a minimum of code bloat.

I offer this to the firing range ;)

Jim
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