[PATCHv2 1/4] x86/mm/ident_map: Fix virtual address wrap to zero

Kirill A. Shutemov
2024-08-14T12:46:22Z

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.

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

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.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);
--
2.43.0