6.6-stable review patch. If anyone has any objections, please let me know.
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From: Ryan Roberts ryan.roberts@arm.com
commit a1d416bf9faf4f4871cb5a943614a07f80a7d70f upstream.
Since commit 38e0edb15bd0 ("mm/apply_to_range: call pte function with lazy updates") it's been possible for arch_[enter|leave]_lazy_mmu_mode() to be called without holding a page table lock (for the kernel mappings case), and therefore it is possible that preemption may occur while in the lazy mmu mode. The Sparc lazy mmu implementation is not robust to preemption since it stores the lazy mode state in a per-cpu structure and does not attempt to manage that state on task switch.
Powerpc had the same issue and fixed it by explicitly disabling preemption in arch_enter_lazy_mmu_mode() and re-enabling in arch_leave_lazy_mmu_mode(). See commit b9ef323ea168 ("powerpc/64s: Disable preemption in hash lazy mmu mode").
Given Sparc's lazy mmu mode is based on powerpc's, let's fix it in the same way here.
Link: https://lkml.kernel.org/r/20250303141542.3371656-4-ryan.roberts@arm.com Fixes: 38e0edb15bd0 ("mm/apply_to_range: call pte function with lazy updates") Signed-off-by: Ryan Roberts ryan.roberts@arm.com Acked-by: David Hildenbrand david@redhat.com Acked-by: Andreas Larsson andreas@gaisler.com Acked-by: Juergen Gross jgross@suse.com Cc: Borislav Betkov bp@alien8.de Cc: Boris Ostrovsky boris.ostrovsky@oracle.com Cc: Catalin Marinas catalin.marinas@arm.com Cc: Dave Hansen dave.hansen@linux.intel.com Cc: David S. Miller davem@davemloft.net Cc: "H. Peter Anvin" hpa@zytor.com Cc: Ingo Molnar mingo@redhat.com Cc: Juegren Gross jgross@suse.com Cc: Matthew Wilcow (Oracle) willy@infradead.org Cc: Thomas Gleinxer tglx@linutronix.de Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/sparc/mm/tlb.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/arch/sparc/mm/tlb.c +++ b/arch/sparc/mm/tlb.c @@ -52,8 +52,10 @@ out:
void arch_enter_lazy_mmu_mode(void) { - struct tlb_batch *tb = this_cpu_ptr(&tlb_batch); + struct tlb_batch *tb;
+ preempt_disable(); + tb = this_cpu_ptr(&tlb_batch); tb->active = 1; }
@@ -64,6 +66,7 @@ void arch_leave_lazy_mmu_mode(void) if (tb->tlb_nr) flush_tlb_pending(); tb->active = 0; + preempt_enable(); }
static void tlb_batch_add_one(struct mm_struct *mm, unsigned long vaddr,