From dfaed3e1fa7099de8de4e89cbe7eb9c1bca27dfe Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Wed, 7 Jun 2023 10:56:00 +1000
Subject: [PATCH] powerpc/64s/radix: Fix exit lazy tlb mm switch with irqs
enabled
References: bsc#1194869
Patch-mainline: v6.4
Git-commit: dfaed3e1fa7099de8de4e89cbe7eb9c1bca27dfe
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: a665eec0a22e ("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
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/mm/book3s64/radix_tlb.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/mm/book3s64/radix_tlb.c b/arch/powerpc/mm/book3s64/radix_tlb.c
--- a/arch/powerpc/mm/book3s64/radix_tlb.c
+++ b/arch/powerpc/mm/book3s64/radix_tlb.c
@@ -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(&init_mm);
current->active_mm = &init_mm;
switch_mm_irqs_off(mm, &init_mm, current);
mmdrop(mm);
+ local_irq_restore(flags);
}
/*
--
2.41.0