linux-kernel - [PATCH v5 05/23] powerpc32: Fix pte_offset

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Date:	Wed,  3 Feb 2016 23:53:59 +0100 (CET)
From:	Christophe Leroy <christophe.leroy@....fr>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Scott Wood <oss@...error.net>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v5 05/23] powerpc32: Fix pte_offset_kernel() to return NULL
 for bad pages

The fixmap related functions try to map kernel pages that are
already mapped through Large TLBs. pte_offset_kernel() has to
return NULL for LTLBs, otherwise the caller will try to access
level 2 table which doesn't exist

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
v3: new
v4: no change
v5: no change

 arch/powerpc/include/asm/nohash/32/pgtable.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/nohash/32/pgtable.h b/arch/powerpc/include/asm/nohash/32/pgtable.h
index c82cbf5..e201600 100644
--- a/arch/powerpc/include/asm/nohash/32/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/32/pgtable.h
@@ -309,7 +309,8 @@ static inline void __ptep_set_access_flags(pte_t *ptep, pte_t entry)
 #define pte_index(address)		\
 	(((address) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1))
 #define pte_offset_kernel(dir, addr)	\
-	((pte_t *) pmd_page_vaddr(*(dir)) + pte_index(addr))
+	(pmd_bad(*(dir)) ? NULL : (pte_t *)pmd_page_vaddr(*(dir)) + \
+				  pte_index(addr))
 #define pte_offset_map(dir, addr)		\
 	((pte_t *) kmap_atomic(pmd_page(*(dir))) + pte_index(addr))
 #define pte_unmap(pte)		kunmap_atomic(pte)
-- 
2.1.0