x86: save/restore eflags in context switch

(And reset it on new thread creation)

It turns out that eflags is important to save and restore not just
because of iopl, but due to the magic bits like the NT bit, which we
don't want leaking between different threads.

Tested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index 37a7d2eaf4a0..87f9f60b803b 100644
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -209,6 +209,10 @@ ENTRY(ret_from_fork)
         GET_THREAD_INFO(%ebp)
         popl %eax
         CFI_ADJUST_CFA_OFFSET -4
+        pushl $0x0202                   # Reset kernel eflags
+        CFI_ADJUST_CFA_OFFSET 4
+        popfl
+        CFI_ADJUST_CFA_OFFSET -4
         jmp syscall_exit
         CFI_ENDPROC