[PATCH 5.4,5.10] x86/pkeys: Revert a5eff7259790 ("x86/pkeys: Add PKRU value to init_fpstate")

[PATCH 5.4,5.10] x86/pkeys: Revert a5eff7259790 ("x86/pkeys: Add PKRU value to init_fpstate")

[Thadeu Lima de Souza Cascardo]

From: Thomas Gleixner <tglx@linutronix.de>

Commit b3607269ff57fd3c9690cb25962c5e4b91a0fd3b upstream.

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@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121451.451391598@linutronix.de
Reported-by: RAJESH DASARI <raajeshdasari@gmail.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
---

This has been reported to cause a WARNing since the backport of b81fac906a8f
("x86/fpu: Move FPU initialization into arch_cpu_finalize_init()").

a5eff7259790 was part of 5.2 and no older LTS kernels carry it, so not
necessary on 4.19 or 4.14.

---
 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 fcfe891c1e8e..0c0c2cb038ad 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -450,8 +450,6 @@ 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;
@@ -462,9 +460,6 @@ 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;
 }
 
-- 
2.34.1

Re: [PATCH 5.4,5.10] x86/pkeys: Revert a5eff7259790 ("x86/pkeys: Add PKRU value to init_fpstate")

[Greg KH]

On Thu, Aug 10, 2023 at 12:31:06PM -0300, Thadeu Lima de Souza Cascardo wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
> 
> Commit b3607269ff57fd3c9690cb25962c5e4b91a0fd3b upstream.
> 
> 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@linutronix.de>
> Signed-off-by: Borislav Petkov <bp@suse.de>
> Reviewed-by: Borislav Petkov <bp@suse.de>
> Link: https://lkml.kernel.org/r/20210623121451.451391598@linutronix.de
> Reported-by: RAJESH DASARI <raajeshdasari@gmail.com>
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
> ---
> 
> This has been reported to cause a WARNing since the backport of b81fac906a8f
> ("x86/fpu: Move FPU initialization into arch_cpu_finalize_init()").
> 
> a5eff7259790 was part of 5.2 and no older LTS kernels carry it, so not
> necessary on 4.19 or 4.14.

Now queued up, thanks.

greg k-h