[tip:x86/fpu] x86/fpu: Copy the full header in copy_user_to_xstate()

[tip-bot for Eric Biggers]

Commit-ID:  af2c4322d986a08a6e793b74b83a62b325019c20
Gitweb:     http://git.kernel.org/tip/af2c4322d986a08a6e793b74b83a62b325019c20
Author:     Eric Biggers <ebiggers@xxxxxxxxxx>
AuthorDate: Sun, 24 Sep 2017 12:59:10 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 26 Sep 2017 09:43:47 +0200

x86/fpu: Copy the full header in copy_user_to_xstate()

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

Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Eric Biggers <ebiggers3@xxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Kevin Hao <haokexin@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Michael Halcrow <mhalcrow@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
Cc: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
Cc: kernel-hardening@xxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20170924105913.9157-8-mingo@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/fpu/xstate.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 325db78..0cd7b73 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1199,13 +1199,16 @@ int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
 	int i;
 	u64 xfeatures;
 	u64 allowed_features;
+	struct xstate_header hdr;
 
 	offset = offsetof(struct xregs_state, header);
-	size = sizeof(xfeatures);
+	size = sizeof(hdr);
 
-	if (__copy_from_user(&xfeatures, ubuf + offset, size))
+	if (__copy_from_user(&hdr, ubuf + offset, size))
 		return -EFAULT;
 
+	xfeatures = hdr.xfeatures;
+
 	/*
 	 * Reject if the user sets any disabled or supervisor features:
 	 */