4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Will Deacon <will.deacon@xxxxxxx>
commit d96cc49bff5a7735576cc6f6f111f875d101cec8 upstream.
enter_lazy_tlb is called when a kernel thread rides on the back of
another mm, due to a context switch or an explicit call to unuse_mm
where a call to switch_mm is elided.
In these cases, it's important to keep the saved ttbr value up to date
with the active mm, otherwise we can end up with a stale value which
points to a potentially freed page table.
This patch implements enter_lazy_tlb for arm64, so that the saved ttbr0
is kept up-to-date with the active mm for kernel threads.
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: Vinayak Menon <vinmenon@xxxxxxxxxxxxxx>
Fixes: 39bc88e5e38e9b21 ("arm64: Disable TTBR0_EL1 during normal kernel execution")
Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Reviewed-by: Mark Rutland <mark.rutland@xxxxxxx>
Reported-by: Vinayak Menon <vinmenon@xxxxxxxxxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/include/asm/mmu_context.h | 24 ++++++++++--------------
1 file changed, 10 insertions(+), 14 deletions(-)
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -156,20 +156,6 @@ void check_and_switch_context(struct mm_
#define init_new_context(tsk,mm) ({ atomic64_set(&(mm)->context.id, 0); 0; })
-/*
- * This is called when "tsk" is about to enter lazy TLB mode.
- *
- * mm: describes the currently active mm context
- * tsk: task which is entering lazy tlb
- * cpu: cpu number which is entering lazy tlb
- *
- * tsk->mm will be NULL
- */
-static inline void
-enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
-{
-}
-
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
static inline void update_saved_ttbr0(struct task_struct *tsk,
struct mm_struct *mm)
@@ -193,6 +179,16 @@ static inline void update_saved_ttbr0(st
}
#endif
+static inline void
+enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
+{
+ /*
+ * We don't actually care about the ttbr0 mapping, so point it at the
+ * zero page.
+ */
+ update_saved_ttbr0(tsk, &init_mm);
+}
+
static inline void __switch_mm(struct mm_struct *next)
{
unsigned int cpu = smp_processor_id();