linux-kernel - [PATCH 04/10] x86/fpu: Copy the full state_header in copy_kernel_to

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Date:   Sun, 24 Sep 2017 12:59:07 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Eric Biggers <ebiggers3@...il.com>,
        Andy Lutomirski <luto@...capital.net>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: [PATCH 04/10] x86/fpu: Copy the full state_header in copy_kernel_to_xstate()

From: Eric Biggers <ebiggers@...gle.com>

This is in preparation to verify the full xstate header as supplied by user-space.

Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Kevin Hao <haokexin@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Michael Halcrow <mhalcrow@...gle.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Wanpeng Li <wanpeng.li@...mail.com>
Cc: Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc: kernel-hardening@...ts.openwall.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/fpu/xstate.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 2427aeea33b5..02591b96bb25 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1148,11 +1148,13 @@ int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf)
 	int i;
 	u64 xfeatures;
 	u64 allowed_features;
+	struct xstate_header hdr;
 
 	offset = offsetof(struct xregs_state, header);
-	size = sizeof(xfeatures);
+	size = sizeof(hdr);
 
-	memcpy(&xfeatures, kbuf + offset, size);
+	memcpy(&hdr, kbuf + offset, size);
+	xfeatures = hdr.xfeatures;
 
 	/*
 	 * Reject if the user sets any disabled or supervisor features:
-- 
2.11.0