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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: 2722146eb7 ("x86/fpu: Remove fpu->initialized")
Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Sebastian 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
This commit is contained in:
Christoph Hellwig 2019-06-04 19:54:12 +02:00 committed by Borislav Petkov
parent 71ab8323cc
commit 8d3289f2fa
2 changed files with 4 additions and 4 deletions
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6
arch/x86/include/asm/fpu/internal.h
View File

@ -536,7 +536,7 @@ static inline void __fpregs_load_activate(void)
struct fpu *fpu = &current->thread.fpu;
int cpu = smp_processor_id();
if (WARN_ON_ONCE(current->mm == NULL))
if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
return;
if (!fpregs_state_valid(fpu, cpu)) {
@ -567,11 +567,11 @@ static inline void __fpregs_load_activate(void)
* otherwise.
*
* 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)
{
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))
old_fpu->last_cpu = -1;
else

2
arch/x86/kernel/fpu/core.c
View File

@ -102,7 +102,7 @@ static void __kernel_fpu_begin(void)
kernel_fpu_disable();
if (current->mm) {
if (!(current->flags & PF_KTHREAD)) {
if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {
set_thread_flag(TIF_NEED_FPU_LOAD);
/*