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-rw-r--r--mm/memory.c23
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));