The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x dfaed3e1fa7099de8de4e89cbe7eb9c1bca27dfe # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023062335-earthen-worsening-7910@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

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

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@li... 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

diff --git a/arch/powerpc/mm/book3s64/radix_tlb.c b/arch/powerpc/mm/book3s64/radix_tlb.c index ce804b7bf84e..0bd4866d9824 100644 --- 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_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); }

/*