diff options
| -rw-r--r-- | mm/mseal.c | 51 |
1 files changed, 28 insertions, 23 deletions
diff --git a/mm/mseal.c b/mm/mseal.c index adbcc65e9660..d140f569c4c3 100644 --- a/mm/mseal.c +++ b/mm/mseal.c @@ -38,31 +38,40 @@ out: } /* - * Check for do_mseal: - * 1> start is part of a valid vma. - * 2> end is part of a valid vma. - * 3> No gap (unallocated address) between start and end. - * 4> map is sealable. + * mseal() disallows an input range which contain unmapped ranges (VMA holes). + * + * It disallows unmapped regions from start to end whether they exist at the + * start, in the middle, or at the end of the range, or any combination thereof. + * + * This is because after sealng a range, there's nothing to stop memory mapping + * of ranges in the remaining gaps later, meaning that the user might then + * wrongly consider the entirety of the mseal()'d range to be sealed when it + * in fact isn't. + */ + +/* + * Does the [start, end) range contain any unmapped memory? + * + * We ensure that: + * - start is part of a valid VMA. + * - end is part of a valid VMA. + * - no gap (unallocated memory) exists between start and end. */ -static int check_mm_seal(unsigned long start, unsigned long end) +static bool range_contains_unmapped(struct mm_struct *mm, + unsigned long start, unsigned long end) { struct vm_area_struct *vma; - unsigned long nstart = start; + unsigned long prev_end = start; VMA_ITERATOR(vmi, current->mm, start); - /* going through each vma to check. */ for_each_vma_range(vmi, vma, end) { - if (vma->vm_start > nstart) - /* unallocated memory found. */ - return -ENOMEM; - - if (vma->vm_end >= end) - return 0; + if (vma->vm_start > prev_end) + return true; - nstart = vma->vm_end; + prev_end = vma->vm_end; } - return -ENOMEM; + return prev_end < end; } /* @@ -184,14 +193,10 @@ int do_mseal(unsigned long start, size_t len_in, unsigned long flags) if (mmap_write_lock_killable(mm)) return -EINTR; - /* - * First pass, this helps to avoid - * partial sealing in case of error in input address range, - * e.g. ENOMEM error. - */ - ret = check_mm_seal(start, end); - if (ret) + if (range_contains_unmapped(mm, start, end)) { + ret = -ENOMEM; goto out; + } /* * Second pass, this should success, unless there are errors |