x86/xen: Probe target addresses in set_aliased_prot() before the hypercall

The update_va_mapping hypercall can fail if the VA isn't present
in the guest's page tables.  Under certain loads, this can
result in an OOPS when the target address is in unpopulated vmap
space.

While we're at it, add comments to help explain what's going on.

This isn't a great long-term fix.  This code should probably be
changed to use something like set_memory_ro.

Signed-off-by: Andy Lutomirski <[email protected]>
Cc: Andrew Cooper <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: David Vrabel <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Jan Beulich <[email protected]>
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Sasha Levin <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected] <[email protected]>
Cc: <[email protected]>
Cc: xen-devel <[email protected]>
Link: http://lkml.kernel.org/r/0b0e55b995cda11e7829f140b833ef932fcabe3a.1438291540.git.luto@kernel.org
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions