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

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Date:	Thu, 10 Jul 2014 14:12:19 +0530
From:	Madhusudanan Kandasamy <kmadhu@...ux.vnet.ibm.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: [PATCH V2] powerpc: Fail remap_4k_pfn() if PFN doesn't fit inside
 PTE

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 <kmadhu@...ux.vnet.ibm.com>
---
 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

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