From: Arseny Solokha <asolokha@kb.kras.ru>
Date: Fri, 30 Jan 2015 12:08:27 +0000 (+0700)
Subject: powerpc/mm: bail out early when flushing TLB page
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=0dc294f717d41bfbafc746a7a96a7bc0f114c20c;p=linux.git

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 <asolokha@kb.kras.ru>
Signed-off-by: Scott Wood <scottwood@freescale.com>
---

diff --git a/arch/powerpc/mm/tlb_nohash.c b/arch/powerpc/mm/tlb_nohash.c
index f38ea4df6a855..ab0616b0e6c24 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);