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arm64: SW PAN: Update saved ttbr0 value on enter_lazy_tlb 

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@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Cc: <stable@vger.kernel.org>
Fixes: 39bc88e5e3 ("arm64: Disable TTBR0_EL1 during normal kernel execution")
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Reported-by: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Will Deacon 2017-12-06 10:51:12 +00:00
parent 0adbdfde8c
commit d96cc49bff
1 changed files with 10 additions and 14 deletions
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24
arch/arm64/include/asm/mmu_context.h
View File

@ -156,20 +156,6 @@ void check_and_switch_context(struct mm_struct *mm, unsigned int cpu);
#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(struct task_struct *tsk,
}
#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();