diff --git a/ipc/shm.c b/ipc/shm.c
index 4c28d2d8e305cca5781f02117b55e9b21922bdd0..9162123a7b23c348aca8669c56ea56bfbeacadb6 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -870,6 +870,7 @@ asmlinkage long sys_shmdt(char __user *shmaddr)
 	 * could possibly have landed at. Also cast things to loff_t to
 	 * prevent overflows and make comparisions vs. equal-width types.
 	 */
+	size = PAGE_ALIGN(size);
 	while (vma && (loff_t)(vma->vm_end - addr) <= size) {
 		next = vma->vm_next;