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x86/fpu: Prepare fpu_clone() for dynamically enabled features

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The default portion of the parent's FPU state is saved in a child task.
With dynamic features enabled, the non-default portion is not saved in a
child's fpstate because these register states are defined to be
caller-saved. The new task's fpstate is therefore the default buffer.

Fork inherits the permission of the parent.

Also, do not use memcpy() when TIF_NEED_FPU_LOAD is set because it is
invalid when the parent has dynamic features.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211021225527.10184-11-chang.seok.bae@intel.com
This commit is contained in:
Thomas Gleixner
2021-10-21 15:55:14 -07:00
committed by Borislav Petkov
parent 53599b4d54
commit 9e798e9aa1
3 changed files with 27 additions and 12 deletions
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2
arch/x86/kernel/process.c
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@@ -157,7 +157,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
frame->flags = X86_EFLAGS_FIXED;
#endif
fpu_clone(p);
fpu_clone(p, clone_flags);
/* Kernel thread ? */
if (unlikely(p->flags & PF_KTHREAD)) {