Commit 7f88f88f authored by Catalin Marinas's avatar Catalin Marinas Committed by Linus Torvalds
Browse files

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



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: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 81556b02

mm/kmemleak.c

+3 −1
Original line number Diff line number Diff line
@@ -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);

mm/vmalloc.c

+10 −4
Original line number Diff line number Diff line
@@ -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);

	/*
@@ -1645,11 +1651,11 @@ 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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