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    Subject[tip:x86/fpu] x86/fpu/xstate: Return NULL for disabled xstate component address
    Commit-ID:  5060b91513b866f774da15dfd82157864c4b1683
    Gitweb: http://git.kernel.org/tip/5060b91513b866f774da15dfd82157864c4b1683
    Author: Yu-cheng Yu <yu-cheng.yu@intel.com>
    AuthorDate: Mon, 11 Jul 2016 09:18:55 -0700
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Mon, 11 Jul 2016 16:44:00 +0200

    x86/fpu/xstate: Return NULL for disabled xstate component address

    It is an error to request a disabled XSAVE/XSAVES component address.
    For that case, make __raw_xsave_addr() return a NULL and issue a
    warning.

    Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
    Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
    Reviewed-by: Dave Hansen <dave.hansen@intel.com>
    Cc: H. Peter Anvin <h.peter.anvin@intel.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Ravi V Shankar <ravi.v.shankar@intel.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Link: http://lkml.kernel.org/r/1468253937-40008-3-git-send-email-fenghua.yu@intel.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    arch/x86/kernel/fpu/xstate.c | 5 +++++
    1 file changed, 5 insertions(+)

    diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
    index f8d1aff..4fb8dd7 100644
    --- a/arch/x86/kernel/fpu/xstate.c
    +++ b/arch/x86/kernel/fpu/xstate.c
    @@ -760,6 +760,11 @@ void *__raw_xsave_addr(struct xregs_state *xsave, int xstate_feature_mask)
    {
    int feature_nr = fls64(xstate_feature_mask) - 1;

    + if (!xfeature_enabled(feature_nr)) {
    + WARN_ON_FPU(1);
    + return NULL;
    + }
    +
    return (void *)xsave + xstate_comp_offsets[feature_nr];
    }
    /*
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