x86/fpu: Mask PKRU from kernel XRSTOR[S] operations

As the PKRU state is managed separately restoring it from the xstate
buffer would be counterproductive as it might either restore a stale
value or reinit the PKRU state to 0.

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/20210623121456.606745195@linutronix.de

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 5217743..2a484f5 100644 (file)
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -259,7 +259,7 @@ static inline void fxsave(struct fxregs_state *fx)
  */
 static inline void os_xrstor_booting(struct xregs_state *xstate)
 {
-       u64 mask = -1;
+       u64 mask = xfeatures_mask_fpstate();
        u32 lmask = mask;
        u32 hmask = mask >> 32;
        int err;
@@ -388,7 +388,7 @@ extern void __restore_fpregs_from_fpstate(union fpregs_state *fpstate, u64 mask)
 
 static inline void restore_fpregs_from_fpstate(union fpregs_state *fpstate)
 {
-       __restore_fpregs_from_fpstate(fpstate, -1);
+       __restore_fpregs_from_fpstate(fpstate, xfeatures_mask_fpstate());
 }
 
 extern int copy_fpstate_to_sigframe(void __user *buf, void __user *fp, int size);

diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index 4ff4a00..109dfcc 100644 (file)
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -111,6 +111,16 @@ static inline u64 xfeatures_mask_restore_user(void)
        return xfeatures_mask_all & XFEATURE_MASK_USER_RESTORE;
 }
 
+/*
+ * Like xfeatures_mask_restore_user() but additionally restors the
+ * supported supervisor states.
+ */
+static inline u64 xfeatures_mask_fpstate(void)
+{
+       return xfeatures_mask_all & \
+               (XFEATURE_MASK_USER_RESTORE | XFEATURE_MASK_SUPERVISOR_SUPPORTED);
+}
+
 static inline u64 xfeatures_mask_independent(void)
 {
        if (!boot_cpu_has(X86_FEATURE_ARCH_LBR))

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 9fd124a..21a10a6 100644 (file)
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -60,6 +60,7 @@ static short xsave_cpuid_features[] __initdata = {
  * XSAVE buffer, both supervisor and user xstates.
  */
 u64 xfeatures_mask_all __ro_after_init;
+EXPORT_SYMBOL_GPL(xfeatures_mask_all);
 
 static unsigned int xstate_offsets[XFEATURE_MAX] __ro_after_init =
        { [ 0 ... XFEATURE_MAX - 1] = -1};

diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 2c5cccd..e1664e9 100644 (file)
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -65,7 +65,7 @@ __visible bool ex_handler_fprestore(const struct exception_table_entry *fixup,
        WARN_ONCE(1, "Bad FPU state detected at %pB, reinitializing FPU registers.",
                  (void *)instruction_pointer(regs));
 
-       __restore_fpregs_from_fpstate(&init_fpstate, -1);
+       __restore_fpregs_from_fpstate(&init_fpstate, xfeatures_mask_fpstate());
        return true;
 }
 EXPORT_SYMBOL_GPL(ex_handler_fprestore);