mm: kmemleak: avoid false negatives on vmalloc'ed objects

commit 7f88f88f83ed609650a01b18572e605ea50cd163 upstream.

Commit 248ac0e1943a ("mm/vmalloc: remove guard page from between vmap
blocks") had the side effect of making vmap_area.va_end member point to
the next vmap_area.va_start.  This was creating an artificial reference
to vmalloc'ed objects and kmemleak was rarely reporting vmalloc() leaks.

This patch marks the vmap_area containing pointers explicitly and
reduces the min ref_count to 2 as vm_struct still contains a reference
to the vmalloc'ed object.  The kmemleak add_scan_area() function has
been improved to allow a SIZE_MAX argument covering the rest of the
object (for simpler calling sites).

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index f3b2a00..cc8cf1d 100644 (file)
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -744,7 +744,9 @@ static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp)
        }
 
        spin_lock_irqsave(&object->lock, flags);
-       if (ptr + size > object->pointer + object->size) {
+       if (size == SIZE_MAX) {
+               size = object->pointer + object->size - ptr;
+       } else if (ptr + size > object->pointer + object->size) {
                kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
                dump_object_info(object);
                kmem_cache_free(scan_area_cache, area);

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index eeba3bb..1431458 100644 (file)
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -349,6 +349,12 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
        if (unlikely(!va))
                return ERR_PTR(-ENOMEM);
 
+       /*
+        * Only scan the relevant parts containing pointers to other objects
+        * to avoid false negatives.
+        */
+       kmemleak_scan_area(&va->rb_node, SIZE_MAX, gfp_mask & GFP_RECLAIM_MASK);
+
 retry:
        spin_lock(&vmap_area_lock);
        /*
@@ -1644,11 +1650,11 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
        insert_vmalloc_vmlist(area);
 
        /*
-        * A ref_count = 3 is needed because the vm_struct and vmap_area
-        * structures allocated in the __get_vm_area_node() function contain
-        * references to the virtual address of the vmalloc'ed block.
+        * A ref_count = 2 is needed because vm_struct allocated in
+        * __get_vm_area_node() contains a reference to the virtual address of
+        * the vmalloc'ed block.
         */
-       kmemleak_alloc(addr, real_size, 3, gfp_mask);
+       kmemleak_alloc(addr, real_size, 2, gfp_mask);
 
        return addr;