slub: Add method to verify memory is not freed

This is for tracking down suspect memory usage.

Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

1 files changed, 36 insertions, 0 deletions

diff --git a/mm/slub.c b/mm/slub.c
index c9050995bc87..0e4f4f8245bc 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2964,6 +2964,42 @@ size_t ksize(const void *object)
 }
 EXPORT_SYMBOL(ksize);
 
+#ifdef CONFIG_SLUB_DEBUG
+bool verify_mem_not_deleted(const void *x)
+{
+        struct page *page;
+        void *object = (void *)x;
+        unsigned long flags;
+        bool rv;
+
+        if (unlikely(ZERO_OR_NULL_PTR(x)))
+                return false;
+
+        local_irq_save(flags);
+
+        page = virt_to_head_page(x);
+        if (unlikely(!PageSlab(page))) {
+                /* maybe it was from stack? */
+                rv = true;
+                goto out_unlock;
+        }
+
+        slab_lock(page);
+        if (on_freelist(page->slab, page, object)) {
+                object_err(page->slab, page, object, "Object is on free-list");
+                rv = false;
+        } else {
+                rv = true;
+        }
+        slab_unlock(page);
+
+out_unlock:
+        local_irq_restore(flags);
+        return rv;
+}
+EXPORT_SYMBOL(verify_mem_not_deleted);
+#endif
+
 void kfree(const void *x)
 {
         struct page *page;