linux-kernel - [PATCH V3] powerpc : Fail remap_4k_pfn() if PFN doesn't fit inside PTE

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Message-ID: <53BEAE01.7000401@linux.vnet.ibm.com>
Date:	Thu, 10 Jul 2014 20:45:13 +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
Subject: [PATCH V3] 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.

V3 : Added parentheses to protect 'pfn' and entire macro as suggested by Brian.
V2 : Rewritten to avoid helper function as suggested by Stephen Rothwell.

Signed-off-by: Madhusudanan Kandasamy <kmadhu@...ux.vnet.ibm.com>
---
 arch/powerpc/include/asm/pte-hash64-64k.h | 5 +++--
 1 file changed, 3 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..b6d2d42 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,		\
-			__pgprot(pgprot_val((prot)) | _PAGE_4K_PFN))
+	(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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