Re: [patch V2 20/52] x86/fpu: Cleanup arch_set_user_pkey_access()

Borislav Petkov
2021-06-17T12:22:24Z

On Mon, Jun 14, 2021 at 05:44:28PM +0200, Thomas Gleixner wrote:
> The function is having a sanity check with a WARN_ON_ONCE() but happily

"The function does a sanity check..."

> proceeds when the pkey argument is out of range.
>
> Clean it up.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> arch/x86/kernel/fpu/xstate.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> --- a/arch/x86/kernel/fpu/xstate.c
> +++ b/arch/x86/kernel/fpu/xstate.c
> @@ -887,11 +887,10 @@ EXPORT_SYMBOL_GPL(get_xsave_addr);
> * rights for @pkey to @init_val.
> */
> int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
> - unsigned long init_val)
> + unsigned long init_val)
> {
> - u32 old_pkru;
> - int pkey_shift = (pkey * PKRU_BITS_PER_PKEY);
> - u32 new_pkru_bits = 0;
> + u32 old_pkru, new_pkru_bits = 0;
> + int pkey_shift;
>
> /*
> * This check implies XSAVE support. OSPKE only gets

There's a boot_cpu_has() check

<--- here

Might wanna convert it to cpu_feature_enabled(), while at it.

> @@ -905,7 +904,8 @@ int arch_set_user_pkey_access(struct tas
> * values originating from in-kernel users. Complain
> * if a bad value is observed.
> */
> - WARN_ON_ONCE(pkey >= arch_max_pkey());
> + if (WARN_ON_ONCE(pkey >= arch_max_pkey()))
> + return -EINVAL;
>
> /* Set the bits we need in PKRU: */
> if (init_val & PKEY_DISABLE_ACCESS)
> @@ -914,6 +914,7 @@ int arch_set_user_pkey_access(struct tas
> new_pkru_bits |= PKRU_WD_BIT;
>
> /* Shift the bits in to the correct place in PKRU for pkey: */
> + pkey_shift = pkey * PKRU_BITS_PER_PKEY;
> new_pkru_bits <<= pkey_shift;
>
> /* Get old PKRU and mask off any old bits in place: */

With those addressed:

Reviewed-by: Borislav Petkov <bp@suse.de>

--
Regards/Gruss,
Boris.

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