Commit dfaed3e1 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

powerpc/64s/radix: Fix exit lazy tlb mm switch with irqs enabled 



Switching mm and tinkering with current->active_mm should be done with
irqs disabled. There is a path where exit_lazy_flush_tlb can be called
with irqs enabled:

    exit_lazy_flush_tlb
    flush_type_needed
    __flush_all_mm
    tlb_finish_mmu
    exit_mmap

Which results in the switching being done with irqs enabled, which is
incorrect.

Fixes: a665eec0 ("powerpc/64s/radix: Fix mm_cpumask trimming race vs kthread_use_mm")
Cc: stable@vger.kernel.org # v5.10+
Reported-by: default avatarSachin Sant <sachinp@linux.ibm.com>
Link: https://lore.kernel.org/linuxppc-dev/A9A5D83D-BA70-47A4-BCB4-30C1AE19BC22@linux.ibm.com/


Tested-by: default avatarSachin Sant <sachinp@linux.ibm.com>
Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230607005601.583293-1-npiggin@gmail.com
parent 719dfd59

arch/powerpc/mm/book3s64/radix_tlb.c

+9 −1
Original line number Diff line number Diff line
@@ -795,12 +795,20 @@ void exit_lazy_flush_tlb(struct mm_struct *mm, bool always_flush) 
		goto out;



	if (current->active_mm == mm) {

		unsigned long flags;



		WARN_ON_ONCE(current->mm != NULL);

		/* Is a kernel thread and is using mm as the lazy tlb */

		/*

		 * It is a kernel thread and is using mm as the lazy tlb, so

		 * switch it to init_mm. This is not always called from IPI

		 * (e.g., flush_type_needed), so must disable irqs.

		 */

		local_irq_save(flags);

		mmgrab_lazy_tlb(&init_mm);

		current->active_mm = &init_mm;

		switch_mm_irqs_off(mm, &init_mm, current);

		mmdrop_lazy_tlb(mm);

		local_irq_restore(flags);

	}



	/*