From 0dc294f717d41bfbafc746a7a96a7bc0f114c20c Mon Sep 17 00:00:00 2001 From: Arseny Solokha Date: Fri, 30 Jan 2015 19:08:27 +0700 Subject: [PATCH] powerpc/mm: bail out early when flushing TLB page 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 Signed-off-by: Scott Wood --- arch/powerpc/mm/tlb_nohash.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/mm/tlb_nohash.c b/arch/powerpc/mm/tlb_nohash.c index f38ea4df6a85..ab0616b0e6c2 100644 --- a/arch/powerpc/mm/tlb_nohash.c +++ b/arch/powerpc/mm/tlb_nohash.c @@ -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); -- 2.34.1