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Subject[PATCH 03/14] kmemleak: Add the slab memory allocation/freeing hooks
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This patch adds the callbacks to kmemleak_(alloc|free) functions from
the slab allocator. The patch also adds the SLAB_NOLEAKTRACE flag to
avoid recursive calls to kmemleak when it allocates its own data
structures.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
---
include/linux/slab.h | 2 ++
mm/slab.c | 33 +++++++++++++++++++++++++++++++--
2 files changed, 33 insertions(+), 2 deletions(-)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 000da12..d72ad0b 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -62,6 +62,8 @@
# define SLAB_DEBUG_OBJECTS 0x00000000UL
#endif

+#define SLAB_NOLEAKTRACE 0x00800000UL /* Avoid kmemleak tracing */
+
/* The following flags affect the page allocator grouping pages by mobility */
#define SLAB_RECLAIM_ACCOUNT 0x00020000UL /* Objects are reclaimable */
#define SLAB_TEMPORARY SLAB_RECLAIM_ACCOUNT /* Objects are short-lived */
diff --git a/mm/slab.c b/mm/slab.c
index 0918751..ddedd5d 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -106,6 +106,7 @@
#include <linux/string.h>
#include <linux/uaccess.h>
#include <linux/nodemask.h>
+#include <linux/kmemleak.h>
#include <linux/mempolicy.h>
#include <linux/mutex.h>
#include <linux/fault-inject.h>
@@ -177,13 +178,13 @@
SLAB_STORE_USER | \
SLAB_RECLAIM_ACCOUNT | SLAB_PANIC | \
SLAB_DESTROY_BY_RCU | SLAB_MEM_SPREAD | \
- SLAB_DEBUG_OBJECTS)
+ SLAB_DEBUG_OBJECTS | SLAB_NOLEAKTRACE)
#else
# define CREATE_MASK (SLAB_HWCACHE_ALIGN | \
SLAB_CACHE_DMA | \
SLAB_RECLAIM_ACCOUNT | SLAB_PANIC | \
SLAB_DESTROY_BY_RCU | SLAB_MEM_SPREAD | \
- SLAB_DEBUG_OBJECTS)
+ SLAB_DEBUG_OBJECTS | SLAB_NOLEAKTRACE)
#endif

/*
@@ -955,6 +956,14 @@ static struct array_cache *alloc_arraycache(int node, int entries,
struct array_cache *nc = NULL;

nc = kmalloc_node(memsize, GFP_KERNEL, node);
+ /*
+ * The array_cache structures contain pointers to free object.
+ * However, when such objects are allocated or transfered to another
+ * cache the pointers are not cleared and they could be counted as
+ * valid references during a kmemleak scan. Therefore, kmemleak must
+ * not scan such objects.
+ */
+ kmemleak_no_scan(nc);
if (nc) {
nc->avail = 0;
nc->limit = entries;
@@ -2610,6 +2619,15 @@ static struct slab *alloc_slabmgmt(struct kmem_cache *cachep, void *objp,
/* Slab management obj is off-slab. */
slabp = kmem_cache_alloc_node(cachep->slabp_cache,
local_flags & ~GFP_THISNODE, nodeid);
+ /*
+ * If the first object in the slab is leaked (it's allocated
+ * but no one has a reference to it), we want to make sure
+ * kmemleak does not treat the ->s_mem pointer as a reference
+ * to the object. Otherwise we will not report the leak.
+ */
+ kmemleak_scan_area(slabp, offsetof(struct slab, list),
+ sizeof(struct list_head),
+ local_flags & ~GFP_THISNODE);
if (!slabp)
return NULL;
} else {
@@ -3195,6 +3213,12 @@ static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
STATS_INC_ALLOCMISS(cachep);
objp = cache_alloc_refill(cachep, flags);
}
+ /*
+ * To avoid a false negative, if an object that is in one of the
+ * per-CPU caches is leaked, we need to make sure kmemleak doesn't
+ * treat the array pointers as a reference to the object.
+ */
+ kmemleak_erase(&ac->entry[ac->avail]);
return objp;
}

@@ -3412,6 +3436,8 @@ __cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid,
out:
local_irq_restore(save_flags);
ptr = cache_alloc_debugcheck_after(cachep, flags, ptr, caller);
+ kmemleak_alloc_recursive(ptr, obj_size(cachep), 1, cachep->flags,
+ flags);

if (unlikely((flags & __GFP_ZERO) && ptr))
memset(ptr, 0, obj_size(cachep));
@@ -3465,6 +3491,8 @@ __cache_alloc(struct kmem_cache *cachep, gfp_t flags, void *caller)
objp = __do_cache_alloc(cachep, flags);
local_irq_restore(save_flags);
objp = cache_alloc_debugcheck_after(cachep, flags, objp, caller);
+ kmemleak_alloc_recursive(objp, obj_size(cachep), 1, cachep->flags,
+ flags);
prefetchw(objp);

if (unlikely((flags & __GFP_ZERO) && objp))
@@ -3580,6 +3608,7 @@ static inline void __cache_free(struct kmem_cache *cachep, void *objp)
struct array_cache *ac = cpu_cache_get(cachep);

check_irq_off();
+ kmemleak_free_recursive(objp, cachep->flags);
objp = cache_free_debugcheck(cachep, objp, __builtin_return_address(0));

/*


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