[tip: x86/fpu] x86/fpu/xstate: Warn when checking alignment of disabled xfeatures

[tip-bot2 for Yu-cheng Yu]

The following commit has been merged into the x86/fpu branch of tip:

Commit-ID:     e70b100806d63fb79775858ea92e1a716da46186
Gitweb:        https://git.kernel.org/tip/e70b100806d63fb79775858ea92e1a716da46186
Author:        Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
AuthorDate:    Thu, 09 Jan 2020 13:14:52 -08:00
Committer:     Borislav Petkov <bp@xxxxxxx>
CommitterDate: Wed, 12 Feb 2020 15:43:34 +01:00

x86/fpu/xstate: Warn when checking alignment of disabled xfeatures

An XSAVES component's alignment/offset is meaningful only when the
feature is enabled. Return zero and WARN_ONCE on checking alignment of
disabled features.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200109211452.27369-4-yu-cheng.yu@xxxxxxxxx
---
 arch/x86/kernel/fpu/xstate.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index edcaacd..73fe597 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -325,6 +325,13 @@ static int xfeature_is_aligned(int xfeature_nr)
 	u32 eax, ebx, ecx, edx;
 
 	CHECK_XFEATURE(xfeature_nr);
+
+	if (!xfeature_enabled(xfeature_nr)) {
+		WARN_ONCE(1, "Checking alignment of disabled xfeature %d\n",
+			  xfeature_nr);
+		return 0;
+	}
+
 	cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 	/*
 	 * The value returned by ECX[1] indicates the alignment