[tip:x86/fpu] x86/fpu: Eliminate the 'xfeatures' local variable in copy_user_to_xstate()

[tip-bot for Eric Biggers]

Commit-ID:  3d703477bcfe8bb57079d97198cf1e342fe1fef9
Gitweb:     http://git.kernel.org/tip/3d703477bcfe8bb57079d97198cf1e342fe1fef9
Author:     Eric Biggers <ebiggers@xxxxxxxxxx>
AuthorDate: Sun, 24 Sep 2017 12:59:11 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 26 Sep 2017 09:43:48 +0200

x86/fpu: Eliminate the 'xfeatures' local variable in copy_user_to_xstate()

We now have this field in hdr.xfeatures.

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/20170924105913.9157-9-mingo@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/fpu/xstate.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 0cd7b73..b6d78b7 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1197,7 +1197,6 @@ int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
 {
 	unsigned int offset, size;
 	int i;
-	u64 xfeatures;
 	u64 allowed_features;
 	struct xstate_header hdr;
 
@@ -1207,20 +1206,18 @@ int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
 	if (__copy_from_user(&hdr, ubuf + offset, size))
 		return -EFAULT;
 
-	xfeatures = hdr.xfeatures;
-
 	/*
 	 * Reject if the user sets any disabled or supervisor features:
 	 */
 	allowed_features = xfeatures_mask & ~XFEATURE_MASK_SUPERVISOR;
 
-	if (xfeatures & ~allowed_features)
+	if (hdr.xfeatures & ~allowed_features)
 		return -EINVAL;
 
 	for (i = 0; i < XFEATURE_MAX; i++) {
 		u64 mask = ((u64)1 << i);
 
-		if (xfeatures & mask) {
+		if (hdr.xfeatures & mask) {
 			void *dst = __raw_xsave_addr(xsave, 1 << i);
 
 			offset = xstate_offsets[i];
@@ -1231,7 +1228,7 @@ int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
 		}
 	}
 
-	if (xfeatures_mxcsr_quirk(xfeatures)) {
+	if (xfeatures_mxcsr_quirk(hdr.xfeatures)) {
 		offset = offsetof(struct fxregs_state, mxcsr);
 		size = MXCSR_AND_FLAGS_SIZE;
 		if (__copy_from_user(&xsave->i387.mxcsr, ubuf + offset, size))
@@ -1247,7 +1244,7 @@ int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
 	/*
 	 * Add back in the features that came in from userspace:
 	 */
-	xsave->header.xfeatures |= xfeatures;
+	xsave->header.xfeatures |= hdr.xfeatures;
 
 	return 0;
 }