ACK: [SRU][F][PATCH 1/1] x86/pkeys: Revert a5eff7259790 ("x86/pkeys: Add PKRU value to init_fpstate")

[Stefan Bader]

On 10.08.23 17:56, Roxana Nicolescu wrote:
> From: Thomas Gleixner <tglx at linutronix.de>
> 
> BugLink: https://bugs.launchpad.net/bugs/2031022
> 
> This cannot work and it's unclear how that ever made a difference.
> 
> init_fpstate.xsave.header.xfeatures is always 0 so get_xsave_addr() will
> always return a NULL pointer, which will prevent storing the default PKRU
> value in init_fpstate.
> 
> Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
> Signed-off-by: Borislav Petkov <bp at suse.de>
> Reviewed-by: Borislav Petkov <bp at suse.de>
> Link: https://lkml.kernel.org/r/20210623121451.451391598@linutronix.de
> (cherry picked from commit b3607269ff57fd3c9690cb25962c5e4b91a0fd3b)
> Signed-off-by: Roxana Nicolescu <roxana.nicolescu at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>
> ---
>   arch/x86/kernel/cpu/common.c | 5 -----
>   arch/x86/mm/pkeys.c          | 6 ------
>   2 files changed, 11 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index 9a91b5706aae..b0ea0c1f44c1 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -449,8 +449,6 @@ static bool pku_disabled;
>   
>   static __always_inline void setup_pku(struct cpuinfo_x86 *c)
>   {
> -	struct pkru_state *pk;
> -
>   	/* check the boot processor, plus compile options for PKU: */
>   	if (!cpu_feature_enabled(X86_FEATURE_PKU))
>   		return;
> @@ -461,9 +459,6 @@ static __always_inline void setup_pku(struct cpuinfo_x86 *c)
>   		return;
>   
>   	cr4_set_bits(X86_CR4_PKE);
> -	pk = get_xsave_addr(&init_fpstate.xsave, XFEATURE_PKRU);
> -	if (pk)
> -		pk->pkru = init_pkru_value;
>   	/*
>   	 * Seting X86_CR4_PKE will cause the X86_FEATURE_OSPKE
>   	 * cpuid bit to be set.  We need to ensure that we
> diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
> index c6f84c0b5d7a..ca77af96033b 100644
> --- a/arch/x86/mm/pkeys.c
> +++ b/arch/x86/mm/pkeys.c
> @@ -10,7 +10,6 @@
>   
>   #include <asm/cpufeature.h>             /* boot_cpu_has, ...            */
>   #include <asm/mmu_context.h>            /* vma_pkey()                   */
> -#include <asm/fpu/internal.h>		/* init_fpstate			*/
>   
>   int __execute_only_pkey(struct mm_struct *mm)
>   {
> @@ -154,7 +153,6 @@ static ssize_t init_pkru_read_file(struct file *file, char __user *user_buf,
>   static ssize_t init_pkru_write_file(struct file *file,
>   		 const char __user *user_buf, size_t count, loff_t *ppos)
>   {
> -	struct pkru_state *pk;
>   	char buf[32];
>   	ssize_t len;
>   	u32 new_init_pkru;
> @@ -177,10 +175,6 @@ static ssize_t init_pkru_write_file(struct file *file,
>   		return -EINVAL;
>   
>   	WRITE_ONCE(init_pkru_value, new_init_pkru);
> -	pk = get_xsave_addr(&init_fpstate.xsave, XFEATURE_PKRU);
> -	if (!pk)
> -		return -EINVAL;
> -	pk->pkru = new_init_pkru;
>   	return count;
>   }
>   

-- 
- Stefan

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