linux-kernel - [PATCH 08/15] x86: Physical address comparisons in fill

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Message-ID: <2c2a71ec844db597f30754dd79faf87c9de0b21f.1738686764.git.maciej.wieczor-retman@intel.com>
Date: Tue,  4 Feb 2025 18:33:49 +0100
From: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
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Subject: [PATCH 08/15] x86: Physical address comparisons in fill_p*d/pte

Calculating page offset returns a pointer without a tag. When comparing
the calculated offset to a tagged page pointer an error is raised
because they are not equal.

Change pointer comparisons to physical address comparisons as to avoid
issues in KASAN that pointer arithmetic would create.

Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
---
 arch/x86/mm/init_64.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index ff253648706f..bb101412424a 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -251,7 +251,7 @@ static p4d_t *fill_p4d(pgd_t *pgd, unsigned long vaddr)
 	if (pgd_none(*pgd)) {
 		p4d_t *p4d = (p4d_t *)spp_getpage();
 		pgd_populate(&init_mm, pgd, p4d);
-		if (p4d != p4d_offset(pgd, 0))
+		if (__pa(p4d) != __pa(p4d_offset(pgd, 0)))
 			printk(KERN_ERR "PAGETABLE BUG #00! %p <-> %p\n",
 			       p4d, p4d_offset(pgd, 0));
 	}
@@ -263,7 +263,7 @@ static pud_t *fill_pud(p4d_t *p4d, unsigned long vaddr)
 	if (p4d_none(*p4d)) {
 		pud_t *pud = (pud_t *)spp_getpage();
 		p4d_populate(&init_mm, p4d, pud);
-		if (pud != pud_offset(p4d, 0))
+		if (__pa(pud) != __pa(pud_offset(p4d, 0)))
 			printk(KERN_ERR "PAGETABLE BUG #01! %p <-> %p\n",
 			       pud, pud_offset(p4d, 0));
 	}
@@ -275,7 +275,7 @@ static pmd_t *fill_pmd(pud_t *pud, unsigned long vaddr)
 	if (pud_none(*pud)) {
 		pmd_t *pmd = (pmd_t *) spp_getpage();
 		pud_populate(&init_mm, pud, pmd);
-		if (pmd != pmd_offset(pud, 0))
+		if (__pa(pmd) != __pa(pmd_offset(pud, 0)))
 			printk(KERN_ERR "PAGETABLE BUG #02! %p <-> %p\n",
 			       pmd, pmd_offset(pud, 0));
 	}
@@ -287,7 +287,7 @@ static pte_t *fill_pte(pmd_t *pmd, unsigned long vaddr)
 	if (pmd_none(*pmd)) {
 		pte_t *pte = (pte_t *) spp_getpage();
 		pmd_populate_kernel(&init_mm, pmd, pte);
-		if (pte != pte_offset_kernel(pmd, 0))
+		if (__pa(pte) != __pa(pte_offset_kernel(pmd, 0)))
 			printk(KERN_ERR "PAGETABLE BUG #03!\n");
 	}
 	return pte_offset_kernel(pmd, vaddr);
-- 
2.47.1