Subject: [PATCH V2] powerpc: Fail remap_4k_pfn() if PFN doesn't fit inside PTE

From: Madhusudanan Kandasamy <[email-masked]>
Date: Thu, 10 Jul 2014 14:12:19 +0530

V2 : Rewritten to avoid helper function as suggested by Stephen Rothwell.
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.

Signed-off-by: Madhusudanan Kandasamy <[email-masked]>
---
 arch/powerpc/include/asm/pte-hash64-64k.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/pte-hash64-64k.h b/arch/powerpc/include/asm/pte-hash64-64k.h
index d836d94..b5178e4 100644
--- a/arch/powerpc/include/asm/pte-hash64-64k.h
+++ b/arch/powerpc/include/asm/pte-hash64-64k.h
@@ -75,7 +75,8 @@
 	(((pte) & _PAGE_COMBO)? MMU_PAGE_4K: MMU_PAGE_64K)

 #define remap_4k_pfn(vma, addr, pfn, prot)				\
-	remap_pfn_range((vma), (addr), (pfn), PAGE_SIZE,		\
+	WARN_ON((pfn >= (1UL << (64 - PTE_RPN_SHIFT)))) ? -EINVAL :	\
+		remap_pfn_range((vma), (addr), (pfn), PAGE_SIZE,	\
 			__pgprot(pgprot_val((prot)) | _PAGE_4K_PFN))

 #endif	/* __ASSEMBLY__ */
-- 
2.0.1