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author | Will Deacon <will.deacon@arm.com> | 2013-02-28 17:47:20 +0100 |
---|---|---|
committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2013-03-03 22:54:13 +0000 |
commit | 37f47e3d62533c931b04cb409f2eb299e6342331 (patch) | |
tree | 346daa43b9edd75249d72a61c429a62cf662da4b | |
parent | d61947a164760ac520cb416768afdf38c33d60e7 (diff) | |
download | op-kernel-dev-37f47e3d62533c931b04cb409f2eb299e6342331.zip op-kernel-dev-37f47e3d62533c931b04cb409f2eb299e6342331.tar.gz |
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: <stable@vger.kernel.org> # 3.8
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
-rw-r--r-- | arch/arm/mm/context.c | 6 |
1 files 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: |