Commit 12f7764a authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Borislav Petkov
Browse files

x86/process: Check PF_KTHREAD and not current->mm for kernel threads 



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: 0cecca9d ("x86/fpu: Eager switch PKRU state")
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Acked-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Acked-by: default avatarRik van Riel <riel@surriel.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210608144345.912645927@linutronix.de
parent d8778e39

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

+1 −1
Original line number Diff line number Diff line
@@ -578,7 +578,7 @@ static inline void switch_fpu_finish(struct fpu *new_fpu) 
	 * 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;