Allow stack to grow up to address space limit

commit bd726c90b6b8ce87602208701b208a208e6d5600 upstream. Fix expand_upwards() on architectures with an upward-growing stack (parisc, metag and partly IA-64) to allow the stack to reliably grow exactly up to the address space limit given by TASK_SIZE. Change-Id: I38c33f932ee0fb408881f198f50361ea063d1c69 Signed-off-by: Helge Deller <[email protected]> Acked-by: Hugh Dickins <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Ben Hutchings <[email protected]> Signed-off-by: Francisco Franco <[email protected]>
franciscofranco · Nov 7, 2017 · 669d408 · 669d408
1 parent 30e7e52
commit 669d408
Showing 1 changed file with 8 additions and 5 deletions.
diff --git a/mm/mmap.c b/mm/mmap.c
@@ -1778,16 +1778,19 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
 	if (!(vma->vm_flags & VM_GROWSUP))
 		return -EFAULT;
 
-	/* Guard against wrapping around to address 0. */
+	/* Guard against exceeding limits of the address space. */
 	address &= PAGE_MASK;
-	address += PAGE_SIZE;
-	if (!address)
+	if (address >= TASK_SIZE)
 		return -ENOMEM;
+	address += PAGE_SIZE;
 
 	/* Enforce stack_guard_gap */
 	gap_addr = address + stack_guard_gap;
-	if (gap_addr < address)
-		return -ENOMEM;
+
+	/* Guard against overflow */
+	if (gap_addr < address || gap_addr > TASK_SIZE)
+		gap_addr = TASK_SIZE;
+
 	next = vma->vm_next;
 	if (next && next->vm_start < gap_addr) {
 		if (!(next->vm_flags & VM_GROWSUP))