Re: [x86] 45fc8757d1: BUG:unable_to_handle_kernel
- Date: Fri, 17 Mar 2017 11:00:44 -0700
- From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
- Subject: Re: [x86] 45fc8757d1: BUG:unable_to_handle_kernel
On Fri, Mar 17, 2017 at 10:49 AM, Linus Torvalds
> The linear address can be used to look up which entry it is. I assume
> the GDT starts at ffffffffff577000, and that this is at offset 0x60
> from that. Whatever descriptor that would be..
Hmm. That should be gdt index 12, aka GDT_ENTRY_TLS_MIN.
I guess user space can set almost anything there. Including setting a
segment type that isn't accessed, and that the CPU will change on the
first actual access.
We do have code to verify the limits and types etc iirc, I guess we
can make sure to set the accessed bit too.