Re: [PATCH 00/10] Enhance /dev/mem to allow read/write of arbitrary

Ingo Molnar
2011-07-01T14:46:41Z

* Christoph Hellwig <hch@infradead.org> wrote:

> On Fri, Jul 01, 2011 at 04:37:35PM +0200, Ingo Molnar wrote:
>
> > After initial modules have loaded i essentially disable crash.ko
> > via /proc/sys/kernel/modules_disabled so rootkits have to work a
> > bit harder than that.
>
> Not sure for fedora as I don'[t have a kernel tree at hand right
> now, but for x86 systems at least RHEL6 has the module built in.
> [...]

Fedora Rawhide has it modular:

# grep CRASH /boot/config-2.6.38-0.rc7.git2.3.fc16.x86_64
CONFIG_CRASH=m

# rpm -ql kernel-2.6.38-0.rc7.git2.3.fc16.x86_64 | grep crash
/lib/modules/2.6.38-0.rc7.git2.3.fc16.x86_64/kernel/drivers/char/crash.ko

> [...] Either way we'll need some way to support crash properly in
> mainline, preferably in a boot-time opt-in way. [...]

Yes, boot-time opt-in was what i suggested.

> [...] I'd tend slightly toward optionally enabling /dev/mem for it
> instead of a separate driver, but if people prefer a different
> route I'm fine, too.

No, sharing the driver is perfectly fine and sane as long as this
weird usage is not enabled widely.

> Note that for normal crash usage read only access is just fine.

That's true as well. Petr?

Thanks,

Ingo