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

We have this information in the xstate_header.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kevin Hao <haokexin@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Halcrow <mhalcrow@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Cc: kernel-hardening@lists.openwall.com
Link: http://lkml.kernel.org/r/20170924105913.9157-6-mingo@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 02591b9..c97c4a9 100644 (file)
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1146,7 +1146,6 @@ int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf)
 {
        unsigned int offset, size;
        int i;
-       u64 xfeatures;
        u64 allowed_features;
        struct xstate_header hdr;
 
@@ -1154,20 +1153,19 @@ int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf)
        size = sizeof(hdr);
 
        memcpy(&hdr, kbuf + offset, size);
-       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];
@@ -1177,7 +1175,7 @@ int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf)
                }
        }
 
-       if (xfeatures_mxcsr_quirk(xfeatures)) {
+       if (xfeatures_mxcsr_quirk(hdr.xfeatures)) {
                offset = offsetof(struct fxregs_state, mxcsr);
                size = MXCSR_AND_FLAGS_SIZE;
                memcpy(&xsave->i387.mxcsr, kbuf + offset, size);
@@ -1192,7 +1190,7 @@ int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf)
        /*
         * Add back in the features that came in from userspace:
         */
-       xsave->header.xfeatures |= xfeatures;
+       xsave->header.xfeatures |= hdr.xfeatures;
 
        return 0;
 }