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Subject[ 09/44] ARM: 7479/1: mm: avoid NULL dereference when flushing gate_vma with VIVT caches
Date
From: Greg KH <gregkh@linuxfoundation.org>

3.0-stable review patch. If anyone has any objections, please let me know.

------------------

From: Will Deacon <will.deacon@arm.com>

commit b74253f78400f9a4b42da84bb1de7540b88ce7c4 upstream.

The vivt_flush_cache_{range,page} functions check that the mm_struct
of the VMA being flushed has been active on the current CPU before
performing the cache maintenance.

The gate_vma has a NULL mm_struct pointer and, as such, will cause a
kernel fault if we try to flush it with the above operations. This
happens during ELF core dumps, which include the gate_vma as it may be
useful for debugging purposes.

This patch adds checks to the VIVT cache flushing functions so that VMAs
with a NULL mm_struct are flushed unconditionally (the vectors page may
be dirty if we use it to store the current TLS pointer).

Reported-by: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Tested-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arm/include/asm/cacheflush.h | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/arch/arm/include/asm/cacheflush.h
+++ b/arch/arm/include/asm/cacheflush.h
@@ -215,7 +215,9 @@ static inline void vivt_flush_cache_mm(s
static inline void
vivt_flush_cache_range(struct vm_area_struct *vma, unsigned long start, unsigned long end)
{
- if (cpumask_test_cpu(smp_processor_id(), mm_cpumask(vma->vm_mm)))
+ struct mm_struct *mm = vma->vm_mm;
+
+ if (!mm || cpumask_test_cpu(smp_processor_id(), mm_cpumask(mm)))
__cpuc_flush_user_range(start & PAGE_MASK, PAGE_ALIGN(end),
vma->vm_flags);
}
@@ -223,7 +225,9 @@ vivt_flush_cache_range(struct vm_area_st
static inline void
vivt_flush_cache_page(struct vm_area_struct *vma, unsigned long user_addr, unsigned long pfn)
{
- if (cpumask_test_cpu(smp_processor_id(), mm_cpumask(vma->vm_mm))) {
+ struct mm_struct *mm = vma->vm_mm;
+
+ if (!mm || cpumask_test_cpu(smp_processor_id(), mm_cpumask(mm))) {
unsigned long addr = user_addr & PAGE_MASK;
__cpuc_flush_user_range(addr, addr + PAGE_SIZE, vma->vm_flags);
}



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