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@xxxxxxxxxxxxxxx>
Reviewed-by: Kai Huang <kai.huang@xxxxxxxxx>
Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
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
