linux-kernel - [PATCHv4, REBASED 1/4] x86/mm/ident_map: Fix virtual address wrap to zero

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Message-ID: <20241016111458.846228-2-kirill.shutemov@linux.intel.com>
Date: Wed, 16 Oct 2024 14:14:55 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Baoquan He <bhe@...hat.com>
Cc: Ard Biesheuvel <ardb@...nel.org>,
	Tom Lendacky <thomas.lendacky@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Sean Christopherson <seanjc@...gle.com>,
	linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Kai Huang <kai.huang@...el.com>
Subject: [PATCHv4, REBASED 1/4] x86/mm/ident_map: Fix virtual address wrap to zero

Calculation of 'next' virtual address doesn't protect against wrapping
to zero. It can result in page table corruption and hang. The
problematic case is possible if user sets high x86_mapping_info::offset.

The wrapping to zero only occurs if the top PGD entry is accessed.
There are no such users in the upstream. Only hibernate_64.c uses
x86_mapping_info::offset, and it operates on the direct mapping range,
which is not the top PGD entry.

Replace manual 'next' calculation with p?d_addr_end() which handles
wrapping correctly.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Reviewed-by: Kai Huang <kai.huang@...el.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
---
 arch/x86/mm/ident_map.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c
index 437e96fb4977..5872f3ee863c 100644
--- a/arch/x86/mm/ident_map.c
+++ b/arch/x86/mm/ident_map.c
@@ -101,9 +101,7 @@ static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page,
 		pmd_t *pmd;
 		bool use_gbpage;
 
-		next = (addr & PUD_MASK) + PUD_SIZE;
-		if (next > end)
-			next = end;
+		next = pud_addr_end(addr, end);
 
 		/* if this is already a gbpage, this portion is already mapped */
 		if (pud_leaf(*pud))
@@ -154,10 +152,7 @@ static int ident_p4d_init(struct x86_mapping_info *info, p4d_t *p4d_page,
 		p4d_t *p4d = p4d_page + p4d_index(addr);
 		pud_t *pud;
 
-		next = (addr & P4D_MASK) + P4D_SIZE;
-		if (next > end)
-			next = end;
-
+		next = p4d_addr_end(addr, end);
 		if (p4d_present(*p4d)) {
 			pud = pud_offset(p4d, 0);
 			result = ident_pud_init(info, pud, addr, next);
@@ -199,10 +194,7 @@ int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
 		pgd_t *pgd = pgd_page + pgd_index(addr);
 		p4d_t *p4d;
 
-		next = (addr & PGDIR_MASK) + PGDIR_SIZE;
-		if (next > end)
-			next = end;
-
+		next = pgd_addr_end(addr, end);
 		if (pgd_present(*pgd)) {
 			p4d = p4d_offset(pgd, 0);
 			result = ident_p4d_init(info, p4d, addr, next);
-- 
2.45.2