linux-kernel - [PATCH] x86/mm: fix lookup_address() to handle physical memory holes in direct mapping

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Date: Fri, 28 Jun 2024 20:52:29 +0000
From: Ashish Kalra <Ashish.Kalra@....com>
To: <dave.hansen@...ux.intel.com>, <luto@...nel.org>, <peterz@...radead.org>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>
CC: <x86@...nel.org>, <hpa@...or.com>, <kirill.shutemov@...ux.intel.com>,
	<rick.p.edgecombe@...el.com>, <mhklinux@...look.com>, <peterx@...hat.com>,
	<jgross@...e.com>, <linux-kernel@...r.kernel.org>, <thomas.lendacky@....com>,
	<linux-coco@...ts.linux.dev>, <jroedel@...e.de>
Subject: [PATCH] x86/mm: fix lookup_address() to handle physical memory holes in direct mapping

From: Ashish Kalra <ashish.kalra@....com>

lookup_address_in_pgd_attr() at pte level it is simply returning
pte_offset_kernel() and there does not seem to be a check for
returning NULL if pte_none().

Fix lookup_address_in_pgd_attr() to add check for pte_none()
after pte_offset_kernel() and return NULL if it is true.

Signed-off-by: Ashish Kalra <ashish.kalra@....com>
---
 arch/x86/mm/pat/set_memory.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 443a97e515c0..be8b5bf3bc3f 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -672,6 +672,7 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address,
 	p4d_t *p4d;
 	pud_t *pud;
 	pmd_t *pmd;
+	pte_t *pte;
 
 	*level = PG_LEVEL_256T;
 	*nx = false;
@@ -717,7 +718,11 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address,
 	*nx |= pmd_flags(*pmd) & _PAGE_NX;
 	*rw &= pmd_flags(*pmd) & _PAGE_RW;
 
-	return pte_offset_kernel(pmd, address);
+	pte = pte_offset_kernel(pmd, address);
+	if (pte_none(*pte))
+		return NULL;
+
+	return pte;
 }
 
 /*
-- 
2.34.1