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    Subject[patch V4 13/65] x86/fpu: Fail ptrace() requests that try to set invalid MXCSR values
    From: Andy Lutomirski <luto@kernel.org>

    There is no benefit from accepting and silently changing an invalid MXCSR
    value supplied via ptrace(). Instead, return -EINVAL on invalid input.

    Signed-off-by: Andy Lutomirski <luto@kernel.org>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    V2: New patch. Picked up from Andy.
    ---
    arch/x86/kernel/fpu/regset.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)
    ---
    --- a/arch/x86/kernel/fpu/regset.c
    +++ b/arch/x86/kernel/fpu/regset.c
    @@ -64,8 +64,9 @@ int xfpregs_set(struct task_struct *targ
    if (ret)
    return ret;

    - /* Mask invalid MXCSR bits (for historical reasons). */
    - newstate.mxcsr &= mxcsr_feature_mask;
    + /* Do not allow an invalid MXCSR value. */
    + if (newstate.mxcsr & ~mxcsr_feature_mask)
    + return -EINVAL;

    fpu__prepare_write(fpu);

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