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Commit 8d3289f2 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Borislav Petkov
Browse files

x86/fpu: Don't use current->mm to check for a kthread 



current->mm can be non-NULL if a kthread calls use_mm(). Check for
PF_KTHREAD instead to decide when to store user mode FP state.

Fixes: 2722146e ("x86/fpu: Remove fpu->initialized")
Reported-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Acked-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Aubrey Li <aubrey.li@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190604175411.GA27477@lst.de
parent 71ab8323

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

+3 −3
Original line number Original line Diff line number Diff line
@@ -536,7 +536,7 @@ static inline void __fpregs_load_activate(void) 
	struct fpu *fpu = &current->thread.fpu;

	struct fpu *fpu = &current->thread.fpu;

	int cpu = smp_processor_id();

	int cpu = smp_processor_id();





	if (WARN_ON_ONCE(current->mm == NULL))

	if (WARN_ON_ONCE(current->flags & PF_KTHREAD))

		return;

		return;





	if (!fpregs_state_valid(fpu, cpu)) {

	if (!fpregs_state_valid(fpu, cpu)) {
@@ -567,11 +567,11 @@ static inline void __fpregs_load_activate(void) 
 * otherwise.

 * otherwise.

 *

 *

 * The FPU context is only stored/restored for a user task and

 * The FPU context is only stored/restored for a user task and

 * ->mm is used to distinguish between kernel and user threads.

 * PF_KTHREAD is used to distinguish between kernel and user threads.

 */

 */

static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu)

static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu)

{

{

	if (static_cpu_has(X86_FEATURE_FPU) && current->mm) {

	if (static_cpu_has(X86_FEATURE_FPU) && !(current->flags & PF_KTHREAD)) {

		if (!copy_fpregs_to_fpstate(old_fpu))

		if (!copy_fpregs_to_fpstate(old_fpu))

			old_fpu->last_cpu = -1;

			old_fpu->last_cpu = -1;

		else

		else

arch/x86/kernel/fpu/core.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -102,7 +102,7 @@ static void __kernel_fpu_begin(void) 




	kernel_fpu_disable();

	kernel_fpu_disable();





	if (current->mm) {

	if (!(current->flags & PF_KTHREAD)) {

		if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {

		if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {

			set_thread_flag(TIF_NEED_FPU_LOAD);

			set_thread_flag(TIF_NEED_FPU_LOAD);

			/*

			/*