Commit 30a304a1 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Borislav Petkov
Browse files

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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121456.606745195@linutronix.de
parent e84ba47e

arch/x86/include/asm/fpu/internal.h

+2 −2
Original line number Diff line number Diff line
@@ -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);

arch/x86/include/asm/fpu/xstate.h

+10 −0
Original line number Diff line number Diff line
@@ -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))

arch/x86/kernel/fpu/xstate.c

+1 −0
Original line number Diff line number Diff line
@@ -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};

arch/x86/mm/extable.c

+1 −1
Original line number Diff line number Diff line
@@ -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);