It's unclear how this ever made any difference because
init_fpstate.xsave.header.xfeatures is always 0 so get_xsave_addr() will
always return a NULL pointer.
Fix this by:
- Creating a propagation function instead of several open coded instances
and invoke it only once after the boot CPU has been initialized and from
the debugfs file write function.
- Set the PKRU feature bit in init_fpstate.xsave.header.xfeatures to make
get_xsave_addr() work which allows to store the default value for real.
- Having the feature bit set also gets rid of copy_init_pkru_to_fpregs()
because now copy_init_fpstate_to_fpregs() already loads the default PKRU
value.
Fixes: a5eff7259790 ("x86/pkeys: Add PKRU value to init_fpstate")
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
V2: New patch
---
arch/x86/include/asm/pkeys.h | 3 ++-
arch/x86/kernel/cpu/bugs.c | 3 +++
arch/x86/kernel/cpu/common.c | 5 -----
arch/x86/kernel/fpu/core.c | 3 ---
arch/x86/mm/pkeys.c | 31 ++++++++++++++-----------------
include/linux/pkeys.h | 2 +-
6 files changed, 20 insertions(+), 27 deletions(-)
--- a/arch/x86/include/asm/pkeys.h
+++ b/arch/x86/include/asm/pkeys.h
@@ -124,7 +124,8 @@ extern int arch_set_user_pkey_access(str
unsigned long init_val);
extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
unsigned long init_val);
-extern void copy_init_pkru_to_fpregs(void);
+
+extern void pkru_propagate_default(void);
static inline int vma_pkey(struct vm_area_struct *vma)
{
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -16,6 +16,7 @@
#include <linux/prctl.h>
#include <linux/sched/smt.h>
#include <linux/pgtable.h>
+#include <linux/pkeys.h>
#include <asm/spec-ctrl.h>
#include <asm/cmdline.h>
@@ -120,6 +121,8 @@ void __init check_bugs(void)
arch_smt_update();
+ pkru_propagate_default();
+
#ifdef CONFIG_X86_32
/*
* Check whether we are able to run this kernel safely on SMP.
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -465,8 +465,6 @@ 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;
@@ -477,9 +475,6 @@ static __always_inline void setup_pku(st
return;
cr4_set_bits(X86_CR4_PKE);
- pk = get_xsave_addr(&init_fpstate.xsave, XFEATURE_PKRU);
- if (pk)
- pk->pkru = init_pkru_value;
/*
* Setting X86_CR4_PKE will cause the X86_FEATURE_OSPKE
* cpuid bit to be set. We need to ensure that we
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -348,9 +348,6 @@ static inline void copy_init_fpstate_to_
copy_kernel_to_fxregs(&init_fpstate.fxsave);
else
copy_kernel_to_fregs(&init_fpstate.fsave);
-
- if (boot_cpu_has(X86_FEATURE_OSPKE))
- copy_init_pkru_to_fpregs();
}
/*
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -125,20 +125,20 @@ u32 init_pkru_value = PKRU_AD_KEY( 1) |
PKRU_AD_KEY(10) | PKRU_AD_KEY(11) | PKRU_AD_KEY(12) |
PKRU_AD_KEY(13) | PKRU_AD_KEY(14) | PKRU_AD_KEY(15);
-/*
- * Called from the FPU code when creating a fresh set of FPU
- * registers. This is called from a very specific context where
- * we know the FPU registers are safe for use and we can use PKRU
- * directly.
- */
-void copy_init_pkru_to_fpregs(void)
+void pkru_propagate_default(void)
{
- u32 init_pkru_value_snapshot = READ_ONCE(init_pkru_value);
+ struct pkru_state *pk;
+
+ if (!boot_cpu_has(X86_FEATURE_OSPKE))
+ return;
/*
- * Override the PKRU state that came from 'init_fpstate'
- * with the baseline from the process.
+ * Force XFEATURE_PKRU to be set in the header otherwise
+ * get_xsave_addr() does not work and it needs to be set
+ * to make XRSTOR(S) load it.
*/
- write_pkru(init_pkru_value_snapshot);
+ init_fpstate.xsave.header.xfeatures |= XFEATURE_MASK_PKRU;
+ pk = get_xsave_addr(&init_fpstate.xsave, XFEATURE_PKRU);
+ pk->pkru = READ_ONCE(init_pkru_value);
}
static ssize_t init_pkru_read_file(struct file *file, char __user *user_buf,
@@ -154,10 +154,9 @@ static ssize_t init_pkru_read_file(struc
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;
+ u32 new_init_pkru;
char buf[32];
ssize_t len;
- u32 new_init_pkru;
len = min(count, sizeof(buf) - 1);
if (copy_from_user(buf, user_buf, len))
@@ -177,10 +176,8 @@ static ssize_t init_pkru_write_file(stru
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;
+
+ pkru_propagate_default();
return count;
}
--- a/include/linux/pkeys.h
+++ b/include/linux/pkeys.h
@@ -44,7 +44,7 @@ static inline bool arch_pkeys_enabled(vo
return false;
}
-static inline void copy_init_pkru_to_fpregs(void)
+static inline void pkru_propagate_default(void)
{
}
