Re: [PATCH] x86: introduce /dev/mem restrictions with a config option

[devzero]

nice !

did you think about some boot-time param , e.g. "insecure-devmem" or something like that?

recompiling kernel is time consuming.....






From: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Subject: [PATCH] x86: introduce /dev/mem restrictions with a config option

This patch introduces a restriction on /dev/mem: Only non-memory can be
read or written unless the newly introduced config option is set.

The X server needs access to /dev/mem for the PCI space, but it doesn't need
access to memory; both the file permissions and SELinux permissions of /dev/mem
just make X effectively super-super powerful. With the exception of the
BIOS area, there's just no valid app that uses /dev/mem on actual memory.
Other popular users of /dev/mem are rootkits and the like.
(note: mmap access of memory via /dev/mem was already not allowed since
a really long time)

People who want to use /dev/mem for kernel debugging can enable the config
option.

The restrictions of this patch have been in the Fedora and RHEL kernels for
at least 4 years without any problems.

Signed-off-by: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
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