From: Oleg Nesterov <oleg@redhat.com>
Date: Tue, 2 Sep 2014 17:57:17 +0000 (+0200)
Subject: x86, fpu: __restore_xstate_sig()->math_state_restore() needs preempt_disable()
X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=b888e3d442069e3107d9b4a43c1321e4d555b6cd;p=linux-edison.git

x86, fpu: __restore_xstate_sig()->math_state_restore() needs preempt_disable()

commit df24fb859a4e200d9324e2974229fbb7adf00aef upstream.

Add preempt_disable() + preempt_enable() around math_state_restore() in
__restore_xstate_sig(). Otherwise __switch_to() after __thread_fpu_begin()
can overwrite fpu->state we are going to restore.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Link: http://lkml.kernel.org/r/20140902175717.GA21649@redhat.com
Reviewed-by: Suresh Siddha <sbsiddha@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index ada87a329ed..92a099fabd5 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -400,8 +400,11 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
 			set_used_math();
 		}
 
-		if (use_eager_fpu())
+		if (use_eager_fpu()) {
+			preempt_disable();
 			math_state_restore();
+			preempt_enable();
+		}
 
 		return err;
 	} else {