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Subject[PATCH] powerpc: Fail remap_4k_pfn() if PFN doesn't fit inside PTE

remap_4k_pfn() silently truncates upper bits of input 4K PFN if
it cannot be contained in PTE. This leads invalid memory mapping
and could result in a system crash when the memory is accessed.
This patch fails remap_4k_pfn() and returns -EINVAL if the input
4K PFN cannot be contained in PTE.
Used a helper inline function in the failure case so that the
remap_4k_pfn() macro can still be used in expression contexts.

Signed-off-by: Madhusudanan Kandasamy <kmadhu@linux.vnet.ibm.com>
---
arch/powerpc/include/asm/pte-hash64-64k.h | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/pte-hash64-64k.h b/arch/powerpc/include/asm/pte-hash64-64k.h
index d836d94..10af7f1 100644
--- a/arch/powerpc/include/asm/pte-hash64-64k.h
+++ b/arch/powerpc/include/asm/pte-hash64-64k.h
@@ -74,8 +74,15 @@
#define pte_pagesize_index(mm, addr, pte) \
(((pte) & _PAGE_COMBO)? MMU_PAGE_4K: MMU_PAGE_64K)

+static inline int bad_4k_pfn(void)
+{
+ WARN_ON(1);
+ return -EINVAL;
+}
+
#define remap_4k_pfn(vma, addr, pfn, prot) \
- remap_pfn_range((vma), (addr), (pfn), PAGE_SIZE, \
- __pgprot(pgprot_val((prot)) | _PAGE_4K_PFN))
+ ((pfn >= (1UL << (64 - PTE_RPN_SHIFT))) ? bad_4k_pfn() : \
+ remap_pfn_range((vma), (addr), (pfn), PAGE_SIZE, \
+ __pgprot(pgprot_val((prot)) | _PAGE_4K_PFN)))

#endif /* __ASSEMBLY__ */
--
2.0.1


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