kernel-aes67/drivers/lguest
Rusty Russell 0d027c01cd lguest: Fix Malicious Guest GDT Host Crash
If a Guest makes hypercall which sets a GDT entry to not present, we
currently set any segment registers using that GDT entry to 0.
Unfortunately, this is not sufficient: there are other ways of
altering GDT entries which will cause a fault.

The correct solution to do what Linux does: let them set any GDT value
they want and handle the #GP when popping causes a fault.  This has
the added benefit of making our Switcher slightly more robust in the
case of any other bugs which cause it to fault.

We kill the Guest if it causes a fault in the Switcher: it's the
Guest's responsibility to make sure it's not using segments when it
changes them.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-08-09 08:14:56 -07:00
..
core.c lguest: Fix Malicious Guest GDT Host Crash 2007-08-09 08:14:56 -07:00
hypercalls.c Provide timespec to guests rather than jiffies clock. 2007-07-28 19:54:33 -07:00
interrupts_and_traps.c lguest: Fix Malicious Guest GDT Host Crash 2007-08-09 08:14:56 -07:00
io.c lguest: documentation VII: FIXMEs 2007-07-26 11:35:17 -07:00
Kconfig Enable lguest drivers in Kconfig 2007-08-06 18:21:15 -07:00
lg.h Provide timespec to guests rather than jiffies clock. 2007-07-28 19:54:33 -07:00
lguest_asm.S lguest: documentation VII: FIXMEs 2007-07-26 11:35:17 -07:00
lguest_bus.c lguest: documentation III: Drivers 2007-07-26 11:35:17 -07:00
lguest_user.c lguest: documentation IV: Launcher 2007-07-26 11:35:17 -07:00
lguest.c lguest: Fix Malicious Guest GDT Host Crash 2007-08-09 08:14:56 -07:00
Makefile lguest: documentation I: Preparation 2007-07-26 11:35:16 -07:00
page_tables.c lguest: documentation VII: FIXMEs 2007-07-26 11:35:17 -07:00
README lguest: documentation I: Preparation 2007-07-26 11:35:16 -07:00
segments.c lguest: Fix Malicious Guest GDT Host Crash 2007-08-09 08:14:56 -07:00
switcher.S lguest: Fix Malicious Guest GDT Host Crash 2007-08-09 08:14:56 -07:00

Welcome, friend reader, to lguest.

Lguest is an adventure, with you, the reader, as Hero.  I can't think of many
5000-line projects which offer both such capability and glimpses of future
potential; it is an exciting time to be delving into the source!

But be warned; this is an arduous journey of several hours or more!  And as we
know, all true Heroes are driven by a Noble Goal.  Thus I offer a Beer (or
equivalent) to anyone I meet who has completed this documentation.

So get comfortable and keep your wits about you (both quick and humorous).
Along your way to the Noble Goal, you will also gain masterly insight into
lguest, and hypervisors and x86 virtualization in general.

Our Quest is in seven parts: (best read with C highlighting turned on)

I) Preparation
	- In which our potential hero is flown quickly over the landscape for a
	  taste of its scope.  Suitable for the armchair coders and other such
	  persons of faint constitution.

II) Guest
	- Where we encounter the first tantalising wisps of code, and come to
	  understand the details of the life of a Guest kernel.

III) Drivers
	- Whereby the Guest finds its voice and become useful, and our
	  understanding of the Guest is completed.

IV) Launcher
	- Where we trace back to the creation of the Guest, and thus begin our
	  understanding of the Host.

V) Host
	- Where we master the Host code, through a long and tortuous journey.
	  Indeed, it is here that our hero is tested in the Bit of Despair.

VI) Switcher
	- Where our understanding of the intertwined nature of Guests and Hosts
	  is completed.

VII) Mastery
	- Where our fully fledged hero grapples with the Great Question:
	  "What next?"

make Preparation!
Rusty Russell.