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@linutronix.de Cc: stable@vger.kernel.org --- 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) { }