linux-kernel - [PATCH 15/19] kernel: convert audit_tree.count from atomic_t to refcount

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Date:   Mon, 20 Feb 2017 12:19:04 +0200
From:   Elena Reshetova <elena.reshetova@...el.com>
To:     linux-kernel@...r.kernel.org
Cc:     cgroups@...r.kernel.org, linux-audit@...hat.com,
        linux-fsdevel@...r.kernel.org, peterz@...radead.org,
        gregkh@...uxfoundation.org, viro@...iv.linux.org.uk, tj@...nel.org,
        mingo@...hat.com, hannes@...xchg.org, lizefan@...wei.com,
        acme@...nel.org, alexander.shishkin@...ux.intel.com,
        paul@...l-moore.com, eparis@...hat.com, akpm@...ux-foundation.org,
        arnd@...db.de, luto@...nel.org,
        Elena Reshetova <elena.reshetova@...el.com>,
        Hans Liljestrand <ishkamiel@...il.com>,
        Kees Cook <keescook@...omium.org>,
        David Windsor <dwindsor@...il.com>
Subject: [PATCH 15/19] kernel: convert audit_tree.count from atomic_t to refcount_t

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@...el.com>
Signed-off-by: Hans Liljestrand <ishkamiel@...il.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: David Windsor <dwindsor@...il.com>
---
 kernel/audit_tree.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index 7b44195..7ed617b 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -9,7 +9,7 @@ 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 +77,7 @@ 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 +91,12 @@ 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);
 }
 
-- 
2.7.4