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audit: convert audit_tree.count from atomic_t to refcount_t

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refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
[PM: fix subject line, add #include]
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Elena Reshetova 2017-05-02 10:16:04 -04:00 committed by Paul Moore
parent 2173c519d5
commit 9d2378f8c8
1 changed files with 5 additions and 4 deletions
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9
kernel/audit_tree.c
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@ -3,13 +3,14 @@
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/kthread.h>
#include <linux/refcount.h>
#include <linux/slab.h>
struct audit_tree;
struct audit_chunk;
struct audit_tree {
atomic_t count;
refcount_t count;
int goner;
struct audit_chunk *root;
struct list_head chunks;
@ -77,7 +78,7 @@ static struct audit_tree *alloc_tree(const char *s)
tree = kmalloc(sizeof(struct audit_tree) + strlen(s) + 1, GFP_KERNEL);
if (tree) {
atomic_set(&tree->count, 1);
refcount_set(&tree->count, 1);
tree->goner = 0;
INIT_LIST_HEAD(&tree->chunks);
INIT_LIST_HEAD(&tree->rules);
@ -91,12 +92,12 @@ static struct audit_tree *alloc_tree(const char *s)
static inline void get_tree(struct audit_tree *tree)
{
atomic_inc(&tree->count);
refcount_inc(&tree->count);
}
static inline void put_tree(struct audit_tree *tree)
{
if (atomic_dec_and_test(&tree->count))
if (refcount_dec_and_test(&tree->count))
kfree_rcu(tree, head);
}