linux-kernel - [PATCH v6 11/13] x86/xsaves: When a disabled xstate component offset is requested, return NULL

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Message-Id: <32f956933af74045ae503ae90437fc83b92d1ba8.1462914897.git.yu-cheng.yu@intel.com>
Date:	Tue, 10 May 2016 16:30:03 -0700
From:	Yu-cheng Yu <yu-cheng.yu@...el.com>
To:	linux-kernel@...r.kernel.org, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
Cc:	Dave Hansen <dave.hansen@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...e.de>,
	Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
	"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: [PATCH v6 11/13] x86/xsaves: When a disabled xstate component offset is requested, return NULL

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>
---
 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 a913d4e..7c2cdc4 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -761,6 +761,11 @@ 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];
 }
 
-- 
1.9.1