Commit dba82d94 authored Sep 23, 2019 by Catalin Marinas Committed by Linus Torvalds Sep 24, 2019

mm: kmemleak: make the tool tolerant to struct scan_area allocation failures

Patch series "mm: kmemleak: Use a memory pool for kmemleak object
allocations", v3.

Following the discussions on v2 of this patch(set) [1], this series takes
slightly different approach:

- it implements its own simple memory pool that does not rely on the
  slab allocator

- drops the early log buffer logic entirely since it can now allocate
  metadata from the memory pool directly before kmemleak is fully
  initialised

- CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE option is renamed to
  CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE

- moves the kmemleak_init() call earlier (mm_init())

- to avoid a separate memory pool for struct scan_area, it makes the
  tool robust when such allocations fail as scan areas are rather an
  optimisation

[1] http://lkml.kernel.org/r/20190727132334.9184-1-catalin.marinas@arm.com

This patch (of 3):

Object scan areas are an optimisation aimed to decrease the false
positives and slightly improve the scanning time of large objects known to
only have a few specific pointers.  If a struct scan_area fails to
allocate, kmemleak can still function normally by scanning the full
object.

Introduce an OBJECT_FULL_SCAN flag and mark objects as such when scan_area
allocation fails.

Link: http://lkml.kernel.org/r/20190812160642.52134-2-catalin.marinas@arm.com


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent b751c52b

mm/kmemleak.c

+10 −6

Original line number	Diff line number	Diff line
		@@ -168,6 +168,8 @@ struct kmemleak_object {
		#define OBJECT_REPORTED (1 << 1)
		/* flag set to not scan the object */
		#define OBJECT_NO_SCAN (1 << 2)
		/* flag set to fully scan the object when scan_area allocation failed */
		#define OBJECT_FULL_SCAN (1 << 3)

		#define HEX_PREFIX " "
		/* number of bytes to print per line; must be 16 or 32 */
		@@ -773,12 +775,14 @@ static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp)
		}

		area = kmem_cache_alloc(scan_area_cache, gfp_kmemleak_mask(gfp));
		if (!area) {
		pr_warn("Cannot allocate a scan area\n");
		goto out;
		}

		spin_lock_irqsave(&object->lock, flags);
		if (!area) {
		pr_warn_once("Cannot allocate a scan area, scanning the full object\n");
		/* mark the object for full scan to avoid false positives */
		object->flags \|= OBJECT_FULL_SCAN;
		goto out_unlock;
		}
		if (size == SIZE_MAX) {
		size = object->pointer + object->size - ptr;
		} else if (ptr + size > object->pointer + object->size) {
		@@ -795,7 +799,6 @@ static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp)
		hlist_add_head(&area->node, &object->area_list);
		out_unlock:
		spin_unlock_irqrestore(&object->lock, flags);
		out:
		put_object(object);
		}

		@@ -1408,7 +1411,8 @@ static void scan_object(struct kmemleak_object *object)
		if (!(object->flags & OBJECT_ALLOCATED))
		/* already freed object */
		goto out;
		if (hlist_empty(&object->area_list)) {
		if (hlist_empty(&object->area_list) \|\|
		object->flags & OBJECT_FULL_SCAN) {
		void start = (void )object->pointer;
		void end = (void )(object->pointer + object->size);
		void *next;

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