Kmemleak requires that vmalloc'ed objects have a minimum reference count
of 2: one in the corresponding vm_struct object and the other owned by
the vmalloc() caller. There are cases, however, where the original
vmalloc() returned pointer is lost and, instead, a pointer to vm_struct
is stored (see free_thread_stack()). Kmemleak currently reports such
objects as leaks.
This patch adds support for treating any surplus references to an object
as additional references to a specified object. It introduces the
kmemleak_vmalloc() API function which takes a vm_struct pointer and sets
its surplus reference passing to the actual vmalloc() returned pointer.
The __vmalloc_node_range() calling site has been modified accordingly.
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: "Luis R. Rodriguez" <mcgrof@xxxxxxxxxx>
Reported-by: "Luis R. Rodriguez" <mcgrof@xxxxxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
---
Documentation/dev-tools/kmemleak.rst | 1 +
include/linux/kmemleak.h | 7 +++
mm/kmemleak.c | 93 ++++++++++++++++++++++++++++++++++--
mm/vmalloc.c | 7 +--
4 files changed, 98 insertions(+), 10 deletions(-)
diff --git a/Documentation/dev-tools/kmemleak.rst b/Documentation/dev-tools/kmemleak.rst
index b2391b829169..cb8862659178 100644
--- a/Documentation/dev-tools/kmemleak.rst
+++ b/Documentation/dev-tools/kmemleak.rst
@@ -150,6 +150,7 @@ See the include/linux/kmemleak.h header for the functions prototype.
- ``kmemleak_init`` - initialize kmemleak
- ``kmemleak_alloc`` - notify of a memory block allocation
- ``kmemleak_alloc_percpu`` - notify of a percpu memory block allocation
+- ``kmemleak_vmalloc`` - notify of a vmalloc() memory allocation
- ``kmemleak_free`` - notify of a memory block freeing
- ``kmemleak_free_part`` - notify of a partial memory block freeing
- ``kmemleak_free_percpu`` - notify of a percpu memory block freeing
diff --git a/include/linux/kmemleak.h b/include/linux/kmemleak.h
index 1c2a32829620..590343f6c1b1 100644
--- a/include/linux/kmemleak.h
+++ b/include/linux/kmemleak.h
@@ -22,6 +22,7 @@
#define __KMEMLEAK_H
#include <linux/slab.h>
+#include <linux/vmalloc.h>
#ifdef CONFIG_DEBUG_KMEMLEAK
@@ -30,6 +31,8 @@ extern void kmemleak_alloc(const void *ptr, size_t size, int min_count,
gfp_t gfp) __ref;
extern void kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
gfp_t gfp) __ref;
+extern void kmemleak_vmalloc(const struct vm_struct *area, size_t size,
+ gfp_t gfp) __ref;
extern void kmemleak_free(const void *ptr) __ref;
extern void kmemleak_free_part(const void *ptr, size_t size) __ref;
extern void kmemleak_free_percpu(const void __percpu *ptr) __ref;
@@ -81,6 +84,10 @@ static inline void kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
gfp_t gfp)
{
}
+static inline void kmemleak_vmalloc(const struct vm_struct *area, size_t size,
+ gfp_t gfp)
+{
+}
static inline void kmemleak_free(const void *ptr)
{
}
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 266482f460c2..7780cd83a495 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -159,6 +159,8 @@ struct kmemleak_object {
atomic_t use_count;
unsigned long pointer;
size_t size;
+ /* pass surplus references to this pointer */
+ unsigned long excess_ref;
/* minimum number of a pointers found before it is considered leak */
int min_count;
/* the total number of pointers found pointing to this object */
@@ -253,7 +255,8 @@ enum {
KMEMLEAK_NOT_LEAK,
KMEMLEAK_IGNORE,
KMEMLEAK_SCAN_AREA,
- KMEMLEAK_NO_SCAN
+ KMEMLEAK_NO_SCAN,
+ KMEMLEAK_SET_EXCESS_REF
};
/*
@@ -264,7 +267,10 @@ struct early_log {
int op_type; /* kmemleak operation type */
int min_count; /* minimum reference count */
const void *ptr; /* allocated/freed memory block */
- size_t size; /* memory block size */
+ union {
+ size_t size; /* memory block size */
+ unsigned long excess_ref; /* surplus reference passing */
+ };
unsigned long trace[MAX_TRACE]; /* stack trace */
unsigned int trace_len; /* stack trace length */
};
@@ -562,6 +568,7 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
object->flags = OBJECT_ALLOCATED;
object->pointer = ptr;
object->size = size;
+ object->excess_ref = 0;
object->min_count = min_count;
object->count = 0; /* white color initially */
object->jiffies = jiffies;
@@ -795,6 +802,30 @@ static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp)
}
/*
+ * Any surplus references (object already gray) to 'ptr' are passed to
+ * 'excess_ref'. This is used in the vmalloc() case where a pointer to
+ * vm_struct may be used as an alternative reference to the vmalloc'ed object
+ * (see free_thread_stack()).
+ */
+static void object_set_excess_ref(unsigned long ptr, unsigned long excess_ref)
+{
+ unsigned long flags;
+ struct kmemleak_object *object;
+
+ object = find_and_get_object(ptr, 0);
+ if (!object) {
+ kmemleak_warn("Setting excess_ref on unknown object at 0x%08lx\n",
+ ptr);
+ return;
+ }
+
+ spin_lock_irqsave(&object->lock, flags);
+ object->excess_ref = excess_ref;
+ spin_unlock_irqrestore(&object->lock, flags);
+ put_object(object);
+}
+
+/*
* Set the OBJECT_NO_SCAN flag for the object corresponding to the give
* pointer. Such object will not be scanned by kmemleak but references to it
* are searched.
@@ -908,7 +939,7 @@ static void early_alloc_percpu(struct early_log *log)
* @gfp: kmalloc() flags used for kmemleak internal memory allocations
*
* This function is called from the kernel allocators when a new object
- * (memory block) is allocated (kmem_cache_alloc, kmalloc, vmalloc etc.).
+ * (memory block) is allocated (kmem_cache_alloc, kmalloc etc.).
*/
void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count,
gfp_t gfp)
@@ -952,6 +983,36 @@ void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
EXPORT_SYMBOL_GPL(kmemleak_alloc_percpu);
/**
+ * kmemleak_vmalloc - register a newly vmalloc'ed object
+ * @area: pointer to vm_struct
+ * @size: size of the object
+ * @gfp: __vmalloc() flags used for kmemleak internal memory allocations
+ *
+ * This function is called from the vmalloc() kernel allocator when a new
+ * object (memory block) is allocated.
+ */
+void __ref kmemleak_vmalloc(const struct vm_struct *area, size_t size, gfp_t gfp)
+{
+ pr_debug("%s(0x%p, %zu)\n", __func__, area, size);
+
+ /*
+ * A min_count = 2 is needed because vm_struct contains a reference to
+ * the virtual address of the vmalloc'ed block.
+ */
+ if (kmemleak_enabled) {
+ create_object((unsigned long)area->addr, size, 2, gfp);
+ object_set_excess_ref((unsigned long)area,
+ (unsigned long)area->addr);
+ } else if (kmemleak_early_log) {
+ log_early(KMEMLEAK_ALLOC, area->addr, size, 2);
+ /* reusing early_log.size for storing area->addr */
+ log_early(KMEMLEAK_SET_EXCESS_REF,
+ area, (unsigned long)area->addr, 0);
+ }
+}
+EXPORT_SYMBOL_GPL(kmemleak_vmalloc);
+
+/**
* kmemleak_free - unregister a previously registered object
* @ptr: pointer to beginning of the object
*
@@ -1248,6 +1309,7 @@ static void scan_block(void *_start, void *_end,
for (ptr = start; ptr < end; ptr++) {
struct kmemleak_object *object;
unsigned long pointer;
+ unsigned long excess_ref;
if (scan_should_stop())
break;
@@ -1283,8 +1345,27 @@ static void scan_block(void *_start, void *_end,
* enclosed by scan_mutex.
*/
spin_lock_nested(&object->lock, SINGLE_DEPTH_NESTING);
- update_refs(object);
+ /* only pass surplus references (object already gray) */
+ if (color_gray(object)) {
+ excess_ref = object->excess_ref;
+ /* no need for update_refs() if object already gray */
+ } else {
+ excess_ref = 0;
+ update_refs(object);
+ }
spin_unlock(&object->lock);
+
+ if (excess_ref) {
+ object = lookup_object(excess_ref, 0);
+ if (!object)
+ continue;
+ if (object == scanned)
+ /* circular reference, ignore */
+ continue;
+ spin_lock_nested(&object->lock, SINGLE_DEPTH_NESTING);
+ update_refs(object);
+ spin_unlock(&object->lock);
+ }
}
read_unlock_irqrestore(&kmemleak_lock, flags);
}
@@ -1987,6 +2068,10 @@ void __init kmemleak_init(void)
case KMEMLEAK_NO_SCAN:
kmemleak_no_scan(log->ptr);
break;
+ case KMEMLEAK_SET_EXCESS_REF:
+ object_set_excess_ref((unsigned long)log->ptr,
+ log->excess_ref);
+ break;
default:
kmemleak_warn("Unknown early log operation: %d\n",
log->op_type);
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 34a1c3e46ed7..b805cc5ecca0 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1759,12 +1759,7 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
*/
clear_vm_uninitialized_flag(area);
- /*
- * 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, 2, gfp_mask);
+ kmemleak_vmalloc(area, size, gfp_mask);
return addr;
--
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