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    Subject[PATCH 08/10] x86/fpu: Eliminate the 'xfeatures' local variable in copy_user_to_xstate()
    Date
    From: Eric Biggers <ebiggers@google.com>

    We now have this field in hdr.xfeatures.

    Signed-off-by: Eric Biggers <ebiggers@google.com>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: Dmitry Vyukov <dvyukov@google.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
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    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 0cd7b73c25e8..b6d78b78b5c2 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;
    }
    --
    2.11.0
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