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    Subject[patch V4 53/65] x86/fpu: Mask PKRU from kernel XRSTOR[S] operations
    As the PKRU state is managed separately restoring it from the xstate buffer
    would be counterproductive as it might either restore a stale value or
    reinit the PKRU state to 0.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Reviewed-by: Borislav Petkov <bp@suse.de>
    ---
    arch/x86/include/asm/fpu/internal.h | 4 ++--
    arch/x86/include/asm/fpu/xstate.h | 10 ++++++++++
    arch/x86/kernel/fpu/xstate.c | 1 +
    arch/x86/mm/extable.c | 2 +-
    4 files changed, 14 insertions(+), 3 deletions(-)

    --- a/arch/x86/include/asm/fpu/internal.h
    +++ b/arch/x86/include/asm/fpu/internal.h
    @@ -259,7 +259,7 @@ static inline void fxsave(struct fxregs_
    */
    static inline void os_xrstor_booting(struct xregs_state *xstate)
    {
    - u64 mask = -1;
    + u64 mask = xfeatures_mask_fpstate();
    u32 lmask = mask;
    u32 hmask = mask >> 32;
    int err;
    @@ -388,7 +388,7 @@ extern void __restore_fpregs_from_fpstat

    static inline void restore_fpregs_from_fpstate(union fpregs_state *fpstate)
    {
    - __restore_fpregs_from_fpstate(fpstate, -1);
    + __restore_fpregs_from_fpstate(fpstate, xfeatures_mask_fpstate());
    }

    extern int copy_fpstate_to_sigframe(void __user *buf, void __user *fp, int size);
    --- a/arch/x86/include/asm/fpu/xstate.h
    +++ b/arch/x86/include/asm/fpu/xstate.h
    @@ -111,6 +111,16 @@ static inline u64 xfeatures_mask_restore
    return xfeatures_mask_all & XFEATURE_MASK_USER_RESTORE;
    }

    +/*
    + * Like xfeatures_mask_restore_user() but additionally restors the
    + * supported supervisor states.
    + */
    +static inline u64 xfeatures_mask_fpstate(void)
    +{
    + return xfeatures_mask_all & \
    + (XFEATURE_MASK_USER_RESTORE | XFEATURE_MASK_SUPERVISOR_SUPPORTED);
    +}
    +
    static inline u64 xfeatures_mask_independent(void)
    {
    if (!boot_cpu_has(X86_FEATURE_ARCH_LBR))
    --- a/arch/x86/kernel/fpu/xstate.c
    +++ b/arch/x86/kernel/fpu/xstate.c
    @@ -60,6 +60,7 @@ static short xsave_cpuid_features[] __in
    * XSAVE buffer, both supervisor and user xstates.
    */
    u64 xfeatures_mask_all __ro_after_init;
    +EXPORT_SYMBOL_GPL(xfeatures_mask_all);

    static unsigned int xstate_offsets[XFEATURE_MAX] __ro_after_init =
    { [ 0 ... XFEATURE_MAX - 1] = -1};
    --- a/arch/x86/mm/extable.c
    +++ b/arch/x86/mm/extable.c
    @@ -65,7 +65,7 @@ EXPORT_SYMBOL_GPL(ex_handler_fault);
    WARN_ONCE(1, "Bad FPU state detected at %pB, reinitializing FPU registers.",
    (void *)instruction_pointer(regs));

    - __restore_fpregs_from_fpstate(&init_fpstate, -1);
    + __restore_fpregs_from_fpstate(&init_fpstate, xfeatures_mask_fpstate());
    return true;
    }
    EXPORT_SYMBOL_GPL(ex_handler_fprestore);
    \
     
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      Last update: 2021-06-23 14:28    [W:4.074 / U:0.076 seconds]
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