Messages in this thread | | | Date | Wed, 27 Aug 2008 12:57:53 -0400 (EDT) | From | Jan Engelhardt <> | Subject | Is SKAS still required for UML |
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Hi,
the UML page at http://user-mode-linux.sourceforge.net/old/skas.html mentions that "The UML kernel is present in the address space of each of its processes, and, by default, is writeable".
I tried to put this to a test, and actually failed to modify the UML kernel/memory image from within it. I had a simple kernel module with 'int val = 2;' and upon loading this, done printk("Val is at %p\n", &val); to get to know the address. A userspace program inside the UML then tried to dereference that address and read the value, but that ended in a segfault. /proc/xxx/maps also does not show the UML kernel being mapped in any process inside the UML. Note that I was running in SKAS0 mode, both host and guest are all 64-bit. Is the NX bit of the 64-bit platform securing things off, or has SKAS3 become sort of obsolete?
Jan
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