commit: 37f47e3d62533c931b04cb409f2eb299e6342331 From: Will Deacon <[email protected]> Date: Thu, 28 Feb 2013 17:47:20 +0100 Subject: ARM: 7658/1: mm: fix race updating mm->context.id on ASID rollover
If a thread triggers an ASID rollover, other threads of the same process must be made to wait until the mm->context.id for the shared mm_struct has been updated to new generation and associated book-keeping (e.g. TLB invalidation) has ben performed. However, there is a *tiny* window where both mm->context.id and the relevant active_asids entry are updated to the new generation, but the TLB flush has not been performed, which could allow another thread to return to userspace with a dirty TLB, potentially leading to data corruption. In reality this will never occur because one CPU would need to perform a context-switch in the time it takes another to do a couple of atomic test/set operations but we should plug the race anyway. This patch moves the active_asids update until after the potential TLB flush on context-switch. Cc: <[email protected]> # 3.8 Reviewed-by: Catalin Marinas <[email protected]> Signed-off-by: Will Deacon <[email protected]> Signed-off-by: Russell King <[email protected]> --- arch/arm/mm/context.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c index 7a05111..03ba181 100644 --- a/arch/arm/mm/context.c +++ b/arch/arm/mm/context.c @@ -207,11 +207,11 @@ void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk) if ((mm->context.id ^ atomic64_read(&asid_generation)) >> ASID_BITS) new_context(mm, cpu); - atomic64_set(&per_cpu(active_asids, cpu), mm->context.id); - cpumask_set_cpu(cpu, mm_cpumask(mm)); - if (cpumask_test_and_clear_cpu(cpu, &tlb_flush_pending)) local_flush_tlb_all(); + + atomic64_set(&per_cpu(active_asids, cpu), mm->context.id); + cpumask_set_cpu(cpu, mm_cpumask(mm)); raw_spin_unlock_irqrestore(&cpu_asid_lock, flags); switch_mm_fastpath: -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
