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

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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: a665eec0a2 ("powerpc/64s/radix: Fix mm_cpumask trimming race vs kthread_use_mm")
Cc: stable@vger.kernel.org # v5.10+
Reported-by: Sachin Sant <sachinp@linux.ibm.com>
Link: https://lore.kernel.org/linuxppc-dev/A9A5D83D-BA70-47A4-BCB4-30C1AE19BC22@linux.ibm.com/
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230607005601.583293-1-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2023-06-07 10:56:00 +10:00 committed by Michael Ellerman
parent 719dfd5925
commit dfaed3e1fa
1 changed files with 9 additions and 1 deletions
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10
arch/powerpc/mm/book3s64/radix_tlb.c
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@ -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);
}
/*