From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com
[ Upstream commit f666c92090a41ac5524dade63ff96b3adcf8c2ab ]
The current calculation of the 'next' virtual address in the page table initialization functions in arch/x86/mm/ident_map.c doesn't protect against wrapping to zero.
This is a theoretical issue that cannot happen currently, the problematic case is possible only if the user sets a high enough x86_mapping_info::offset value - which no current code in the upstream kernel does.
( The wrapping to zero only occurs if the top PGD entry is accessed. There are no such users 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. )
Should such an overflow happen, it can result in page table corruption and a hang.
To future-proof this code, replace the manual 'next' calculation with p?d_addr_end() which handles wrapping correctly.
[ Backporter's note: there's no need to backport this patch. ]
Signed-off-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Ingo Molnar mingo@kernel.org Reviewed-by: Kai Huang kai.huang@intel.com Reviewed-by: Tom Lendacky thomas.lendacky@amd.com Cc: Andy Lutomirski luto@kernel.org Cc: Linus Torvalds torvalds@linux-foundation.org Link: https://lore.kernel.org/r/20241016111458.846228-2-kirill.shutemov@linux.inte... Signed-off-by: Sasha Levin sashal@kernel.org --- 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 fe0b2e66ded93..7adf7001473e7 100644 --- a/arch/x86/mm/ident_map.c +++ b/arch/x86/mm/ident_map.c @@ -28,9 +28,7 @@ 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)) @@ -81,10 +79,7 @@ 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); @@ -126,10 +121,7 @@ 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);