diff options
| -rw-r--r-- | mm/memory.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/mm/memory.c b/mm/memory.c index 858829d06a9..9606ceb3c16 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2760,6 +2760,26 @@ out_release: } /* + * This is like a special single-page "expand_downwards()", + * except we must first make sure that 'address-PAGE_SIZE' + * doesn't hit another vma. + * + * The "find_vma()" will do the right thing even if we wrap + */ +static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned long address) +{ + address &= PAGE_MASK; + if ((vma->vm_flags & VM_GROWSDOWN) && address == vma->vm_start) { + address -= PAGE_SIZE; + if (find_vma(vma->vm_mm, address) != vma) + return -ENOMEM; + + expand_stack(vma, address); + } + return 0; +} + +/* * We enter with non-exclusive mmap_sem (to exclude vma changes, * but allow concurrent faults), and pte mapped but not yet locked. * We return with mmap_sem still held, but pte unmapped and unlocked. @@ -2772,6 +2792,9 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, spinlock_t *ptl; pte_t entry; + if (check_stack_guard_page(vma, address) < 0) + return VM_FAULT_SIGBUS; + if (!(flags & FAULT_FLAG_WRITE)) { entry = pte_mkspecial(pfn_pte(my_zero_pfn(address), vma->vm_page_prot)); |