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powerpc/mm: bail out early when flushing TLB page

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MMU_NO_CONTEXT is conditionally defined as 0 or (unsigned int)-1. However,
in __flush_tlb_page() a corresponding variable is only tested for open
coded 0, which can cause NULL pointer dereference if `mm' argument was
legitimately passed as such.

Bail out early in case the first argument is NULL, thus eliminate confusion
between different values of MMU_NO_CONTEXT and avoid disabling and then
re-enabling preemption unnecessarily.

Signed-off-by: Arseny Solokha <asolokha@kb.kras.ru>
Signed-off-by: Scott Wood <scottwood@freescale.com>
This commit is contained in:
Arseny Solokha 2015-01-30 19:08:27 +07:00 committed by Scott Wood
parent c9111a41dc
commit 0dc294f717
1 changed files with 4 additions and 1 deletions
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5
arch/powerpc/mm/tlb_nohash.c
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@ -284,8 +284,11 @@ void __flush_tlb_page(struct mm_struct *mm, unsigned long vmaddr,
struct cpumask *cpu_mask;
unsigned int pid;
if (unlikely(!mm))
return;
preempt_disable();
pid = mm ? mm->context.id : 0;
pid = mm->context.id;
if (unlikely(pid == MMU_NO_CONTEXT))
goto bail;
cpu_mask = mm_cpumask(mm);