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    Subject[PATCH 2/3] x86/fpu: Fix the init_fpstate size check with the actual size
    Date
    The init_fpstate buffer is statically allocated. Thus, the sanity test was
    established to check whether the pre-allocated buffer is enough for the
    calculated size or not.

    The currently measured size is not strictly relevant. Fix to validate the
    calculated init_fpstate size with the pre-allocated area.

    Also, replace the sanity check function with open code for clarity. The
    abstraction itself and the function naming do not tend to represent simply
    what it does.

    Fixes: 2ae996e0c1a3 ("x86/fpu: Calculate the default sizes independently")
    Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
    Cc: x86@kernel.org
    Cc: linux-kernel@vger.kernel.org
    ---
    arch/x86/kernel/fpu/xstate.c | 24 ++++++------------------
    1 file changed, 6 insertions(+), 18 deletions(-)

    diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
    index f0ce10620ab0..f5ef78633b4c 100644
    --- a/arch/x86/kernel/fpu/xstate.c
    +++ b/arch/x86/kernel/fpu/xstate.c
    @@ -678,20 +678,6 @@ static unsigned int __init get_xsave_size_user(void)
    return ebx;
    }

    -/*
    - * Will the runtime-enumerated 'xstate_size' fit in the init
    - * task's statically-allocated buffer?
    - */
    -static bool __init is_supported_xstate_size(unsigned int test_xstate_size)
    -{
    - if (test_xstate_size <= sizeof(init_fpstate.regs))
    - return true;
    -
    - pr_warn("x86/fpu: xstate buffer too small (%zu < %d), disabling xsave\n",
    - sizeof(init_fpstate.regs), test_xstate_size);
    - return false;
    -}
    -
    static int __init init_xstate_size(void)
    {
    /* Recompute the context size for enabled features: */
    @@ -717,10 +703,6 @@ static int __init init_xstate_size(void)
    kernel_default_size =
    xstate_calculate_size(fpu_kernel_cfg.default_features, compacted);

    - /* Ensure we have the space to store all default enabled features. */
    - if (!is_supported_xstate_size(kernel_default_size))
    - return -EINVAL;
    -
    if (!paranoid_xstate_size_valid(kernel_size))
    return -EINVAL;

    @@ -879,6 +861,12 @@ void __init fpu__init_system_xstate(unsigned int legacy_size)
    init_fpstate.size = fpu_kernel_cfg.max_size;
    init_fpstate.xfeatures = fpu_kernel_cfg.max_features;

    + if (init_fpstate.size > sizeof(init_fpstate.regs)) {
    + pr_warn("x86/fpu: init_fpstate buffer too small (%zu < %d), disabling XSAVE\n",
    + sizeof(init_fpstate.regs), init_fpstate.size);
    + goto out_disable;
    + }
    +
    setup_init_fpu_buf();

    /*
    --
    2.17.1
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