In case of 5-level paging, we don't put any mapping above 47-bit, unless userspace explicitly asked for it.
Userspace can ask for allocation from full address space by specifying hint address above 47-bit. Nicholas noticed that current implementation violates this interface: we can get vma partly in high addresses if we ask for a mapping at very end of 47-bit address space. Let's make sure that, when consider hint address for non-MAP_FIXED mapping, start and end of resulting vma are on the same side of 47-bit border. Signed-off-by: Kirill A. Shutemov <[email protected]> Reported-by: Nicholas Piggin <[email protected]> --- arch/x86/kernel/sys_x86_64.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c index a63fe77b3217..64b1a0d22247 100644 --- a/arch/x86/kernel/sys_x86_64.c +++ b/arch/x86/kernel/sys_x86_64.c @@ -198,11 +198,19 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, /* requesting a specific address */ if (addr) { addr = PAGE_ALIGN(addr); + if (TASK_SIZE - len < addr) + goto get_unmapped_area; + + /* The mapping shouldn't cross DEFAULT_MAP_WINDOW border */ + if ((addr > DEFAULT_MAP_WINDOW) != + (addr + len > DEFAULT_MAP_WINDOW)) + goto get_unmapped_area; + vma = find_vma(mm, addr); - if (TASK_SIZE - len >= addr && - (!vma || addr + len <= vm_start_gap(vma))) + if (!vma || addr + len <= vm_start_gap(vma)) return addr; } +get_unmapped_area: info.flags = VM_UNMAPPED_AREA_TOPDOWN; info.length = len; -- 2.14.2
