x86: Fix non-lazy GS handling in sys_vm86()

x86: Fix non-lazy GS handling in sys_vm86()

commit 3aa6b186f86c5d06d6d92d14311ffed51f091f40 upstream.

This fixes a stack corruption panic or null dereference oops
due to a bad GS in resume_userspace() when returning from
sys_vm86() and calling lockdep_sys_exit().

Only a problem when CONFIG_LOCKDEP and CONFIG_CC_STACKPROTECTOR
enabled.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Cc: H. Peter Anvin <hpa@zytor.com>
LKML-Reference: <1244384628.2323.4.camel@bimbo>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Steven Noonan <steven@uplinklabs.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>