linux-kernel - [PATCH 2/4] x86/fpu/xstate: Return NULL for disabled xstate component address

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Date:	Mon, 11 Jul 2016 09:18:55 -0700
From:	"Fenghua Yu" <fenghua.yu@...el.com>
To:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H. Peter Anvin" <h.peter.anvin@...el.com>,
	"Dave Hansen" <dave.hansen@...el.com>,
	"Ravi V Shankar" <ravi.v.shankar@...el.com>
Cc:	Yu-cheng Yu <yu-cheng.yu@...el.com>,
	"Fenghua Yu" <fenghua.yu@...el.com>, "x86" <x86@...nel.org>,
	"linux-kernel" <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/4] x86/fpu/xstate: Return NULL for disabled xstate component address

From: Yu-cheng Yu <yu-cheng.yu@...el.com>

It is an error to request a disabled XSAVE/XSAVES component address.
For that case, make __raw_xsave_addr() return a NULL and issue a
warning.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
Reviewed-by: Dave Hansen <dave.hansen@...el.com>
---
 arch/x86/kernel/fpu/xstate.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index f8d1aff..4fb8dd7 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -760,6 +760,11 @@ void *__raw_xsave_addr(struct xregs_state *xsave, int xstate_feature_mask)
 {
 	int feature_nr = fls64(xstate_feature_mask) - 1;
 
+	if (!xfeature_enabled(feature_nr)) {
+		WARN_ON_FPU(1);
+		return NULL;
+	}
+
 	return (void *)xsave + xstate_comp_offsets[feature_nr];
 }
 /*
-- 
2.5.0