linux-kernel - [PATCH] powerpc/32: Fix missing NULL pmd check in virt_to

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Message-Id: <b1177cdfc6af74a3e277bba5d9e708c4b3315ebe.1583575707.git.christophe.leroy@c-s.fr>
Date:   Sat,  7 Mar 2020 10:09:15 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, ndesaulniers@...gle.com
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH] powerpc/32: Fix missing NULL pmd check in virt_to_kpte()

Commit 2efc7c085f05 ("powerpc/32: drop get_pteptr()"),
replaced get_pteptr() by virt_to_kpte(). But virt_to_kpte() lacks a
NULL pmd check and returns an invalid non NULL pointer when there
is no page table.

Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
Fixes: 2efc7c085f05 ("powerpc/32: drop get_pteptr()")
Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 arch/powerpc/include/asm/pgtable.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index b80bfd41828d..b1f1d5339735 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -54,7 +54,9 @@ static inline pmd_t *pmd_ptr_k(unsigned long va)
 
 static inline pte_t *virt_to_kpte(unsigned long vaddr)
 {
-	return pte_offset_kernel(pmd_ptr_k(vaddr), vaddr);
+	pmd_t *pmd = pmd_ptr_k(vaddr);
+
+	return pmd_none(*pmd) ? NULL : pte_offset_kernel(pmd, vaddr);
 }
 #endif
 
-- 
2.25.0