Commit 248ac0e1 (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@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
It looks like it's been a while since kmemleak's effectiveness on
catching vmalloc leaks was reduced. Let's see if the reports increase
now.
mm/kmemleak.c | 4 +++-
mm/vmalloc.c | 14 ++++++++++----
2 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 8d84859..ecf1f83 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -753,7 +753,9 @@ 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 1074543..e2be0f8 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -359,6 +359,12 @@ 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);
/*
@@ -1646,11 +1652,11 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
clear_vm_uninitialized_flag(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;
--
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