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[PATCH 09/19] kernel: convert uprobe.ref 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>
---
 kernel/events/uprobes.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index b62d6fe..a4b33f8 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -64,7 +64,7 @@ static struct percpu_rw_semaphore dup_mmap_sem;
 
 struct uprobe {
 	struct rb_node		rb_node;	/* node in the rb tree */
-	atomic_t		ref;
+	refcount_t		ref;
 	struct rw_semaphore	register_rwsem;
 	struct rw_semaphore	consumer_rwsem;
 	struct list_head	pending_list;
@@ -369,13 +369,13 @@ set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long v
 
 static struct uprobe *get_uprobe(struct uprobe *uprobe)
 {
-	atomic_inc(&uprobe->ref);
+	refcount_inc(&uprobe->ref);
 	return uprobe;
 }
 
 static void put_uprobe(struct uprobe *uprobe)
 {
-	if (atomic_dec_and_test(&uprobe->ref))
+	if (refcount_dec_and_test(&uprobe->ref))
 		kfree(uprobe);
 }
 
@@ -457,7 +457,7 @@ static struct uprobe *__insert_uprobe(struct uprobe *uprobe)
 	rb_link_node(&uprobe->rb_node, parent, p);
 	rb_insert_color(&uprobe->rb_node, &uprobes_tree);
 	/* get access + creation ref */
-	atomic_set(&uprobe->ref, 2);
+	refcount_set(&uprobe->ref, 2);
 
 	return u;
 }
-- 
2.7.4

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[PATCH 09/19] kernel: convert uprobe.ref from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-02-20 11:30 +0100

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