diff options
| -rw-r--r-- | arch/x86/include/asm/elf.h | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/sys_x86_64.c | 10 | ||||
| -rw-r--r-- | arch/x86/mm/hugetlbpage.c | 11 | ||||
| -rw-r--r-- | arch/x86/mm/mmap.c | 46 |
4 files changed, 62 insertions, 6 deletions
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index 3a091cea36c5..0d157d2a1e2a 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -309,6 +309,7 @@ static inline int mmap_is_ia32(void) extern unsigned long task_size_32bit(void); extern unsigned long task_size_64bit(int full_addr_space); extern unsigned long get_mmap_base(int is_legacy); +extern bool mmap_address_hint_valid(unsigned long addr, unsigned long len); #ifdef CONFIG_X86_32 diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c index a63fe77b3217..676774b9bb8d 100644 --- a/arch/x86/kernel/sys_x86_64.c +++ b/arch/x86/kernel/sys_x86_64.c @@ -188,6 +188,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, if (len > TASK_SIZE) return -ENOMEM; + /* No address checking. See comment at mmap_address_hint_valid() */ if (flags & MAP_FIXED) return addr; @@ -197,12 +198,15 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, /* requesting a specific address */ if (addr) { - addr = PAGE_ALIGN(addr); + addr &= PAGE_MASK; + if (!mmap_address_hint_valid(addr, len)) + 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; diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c index 8ae0000cbdb3..00b296617ca4 100644 --- a/arch/x86/mm/hugetlbpage.c +++ b/arch/x86/mm/hugetlbpage.c @@ -158,6 +158,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr, if (len > TASK_SIZE) return -ENOMEM; + /* No address checking. See comment at mmap_address_hint_valid() */ if (flags & MAP_FIXED) { if (prepare_hugepage_range(file, addr, len)) return -EINVAL; @@ -165,12 +166,16 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr, } if (addr) { - addr = ALIGN(addr, huge_page_size(h)); + addr &= huge_page_mask(h); + if (!mmap_address_hint_valid(addr, len)) + 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: if (mm->get_unmapped_area == arch_get_unmapped_area) return hugetlb_get_unmapped_area_bottomup(file, addr, len, pgoff, flags); diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index a99679826846..62285fe77b0f 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -174,3 +174,49 @@ const char *arch_vma_name(struct vm_area_struct *vma) return "[mpx]"; return NULL; } + +/** + * mmap_address_hint_valid - Validate the address hint of mmap + * @addr: Address hint + * @len: Mapping length + * + * Check whether @addr and @addr + @len result in a valid mapping. + * + * On 32bit this only checks whether @addr + @len is <= TASK_SIZE. + * + * On 64bit with 5-level page tables another sanity check is required + * because mappings requested by mmap(@addr, 0) which cross the 47-bit + * virtual address boundary can cause the following theoretical issue: + * + * An application calls mmap(addr, 0), i.e. without MAP_FIXED, where @addr + * is below the border of the 47-bit address space and @addr + @len is + * above the border. + * + * With 4-level paging this request succeeds, but the resulting mapping + * address will always be within the 47-bit virtual address space, because + * the hint address does not result in a valid mapping and is + * ignored. Hence applications which are not prepared to handle virtual + * addresses above 47-bit work correctly. + * + * With 5-level paging this request would be granted and result in a + * mapping which crosses the border of the 47-bit virtual address + * space. If the application cannot handle addresses above 47-bit this + * will lead to misbehaviour and hard to diagnose failures. + * + * Therefore ignore address hints which would result in a mapping crossing + * the 47-bit virtual address boundary. + * + * Note, that in the same scenario with MAP_FIXED the behaviour is + * different. The request with @addr < 47-bit and @addr + @len > 47-bit + * fails on a 4-level paging machine but succeeds on a 5-level paging + * machine. It is reasonable to expect that an application does not rely on + * the failure of such a fixed mapping request, so the restriction is not + * applied. + */ +bool mmap_address_hint_valid(unsigned long addr, unsigned long len) +{ + if (TASK_SIZE - len < addr) + return false; + + return (addr > DEFAULT_MAP_WINDOW) == (addr + len > DEFAULT_MAP_WINDOW); +} |