Allow stack to grow up to address space limit

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.

Signed-off-by: Helge Deller <deller@gmx.de>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 5 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index 290b77d9a01e..a5e3dcd75e79 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2230,16 +2230,19 @@ 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))