Messages in this thread Patch in this message | | | Date | Tue, 08 Jun 2021 16:36:20 +0200 | From | Thomas Gleixner <> | Subject | [patch V3 3/6] x86/process: Check PF_KTHREAD and not current->mm for kernel threads |
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switch_fpu_finish() checks current->mm as indicator for kernel threads. That's wrong because kernel threads can temporarily use a mm of a user process via kthread_use_mm().
Check the task flags for PF_KTHREAD instead.
Fixes: 0cecca9d03c9 ("x86/fpu: Eager switch PKRU state") Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Rik van Riel <riel@surriel.com> Cc: stable@vger.kernel.org --- arch/x86/include/asm/fpu/internal.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -578,7 +578,7 @@ static inline void switch_fpu_finish(str * PKRU state is switched eagerly because it needs to be valid before we * return to userland e.g. for a copy_to_user() operation. */ - if (current->mm) { + if (!(current->flags & PF_KTHREAD)) { pk = get_xsave_addr(&new_fpu->state.xsave, XFEATURE_PKRU); if (pk) pkru_val = pk->pkru;
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