1 files changed, 24 insertions, 0 deletions

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 78689cba178f..c5db9a7264d9 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -434,6 +434,27 @@ static void unmap_vmap_area(struct vmap_area *va)
         vunmap_page_range(va->va_start, va->va_end);
 }
 
+static void vmap_debug_free_range(unsigned long start, unsigned long end)
+{
+        /*
+         * Unmap page tables and force a TLB flush immediately if
+         * CONFIG_DEBUG_PAGEALLOC is set. This catches use after free
+         * bugs similarly to those in linear kernel virtual address
+         * space after a page has been freed.
+         *
+         * All the lazy freeing logic is still retained, in order to
+         * minimise intrusiveness of this debugging feature.
+         *
+         * This is going to be *slow* (linear kernel virtual address
+         * debugging doesn't do a broadcast TLB flush so it is a lot
+         * faster).
+         */
+#ifdef CONFIG_DEBUG_PAGEALLOC
+        vunmap_page_range(start, end);
+        flush_tlb_kernel_range(start, end);
+#endif
+}
+
 /*
  * lazy_max_pages is the maximum amount of virtual address space we gather up
  * before attempting to purge with a TLB flush.
@@ -914,6 +935,7 @@ void vm_unmap_ram(const void *mem, unsigned int count)
         BUG_ON(addr & (PAGE_SIZE-1));
 
         debug_check_no_locks_freed(mem, size);
+        vmap_debug_free_range(addr, addr+size);
 
         if (likely(count <= VMAP_MAX_ALLOC))
                 vb_free(mem, size);
@@ -1130,6 +1152,8 @@ struct vm_struct *remove_vm_area(const void *addr)
         if (va && va->flags & VM_VM_AREA) {
                 struct vm_struct *vm = va->private;
                 struct vm_struct *tmp, **p;
+
+                vmap_debug_free_range(va->va_start, va->va_end);
                 free_unmap_vmap_area(va);
                 vm->size -= PAGE_SIZE;