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audit: convert audit_watch.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 10:16:05 -04:00 committed by Paul Moore
parent 9d2378f8c8
commit bd120ded6a
1 changed files with 5 additions and 4 deletions
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9
kernel/audit_watch.c
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@ -28,6 +28,7 @@
#include <linux/fsnotify_backend.h> #include <linux/fsnotify_backend.h>
#include <linux/namei.h> #include <linux/namei.h>
#include <linux/netlink.h> #include <linux/netlink.h>
#include <linux/refcount.h>
#include <linux/sched.h> #include <linux/sched.h>
#include <linux/slab.h> #include <linux/slab.h>
#include <linux/security.h> #include <linux/security.h>
@ -46,7 +47,7 @@
*/ */
struct audit_watch { struct audit_watch {
atomic_t count; /* reference count */ refcount_t count; /* reference count */
dev_t dev; /* associated superblock device */ dev_t dev; /* associated superblock device */
char *path; /* insertion path */ char *path; /* insertion path */
unsigned long ino; /* associated inode number */ unsigned long ino; /* associated inode number */
@ -111,12 +112,12 @@ static inline struct audit_parent *audit_find_parent(struct inode *inode)
void audit_get_watch(struct audit_watch *watch) void audit_get_watch(struct audit_watch *watch)
{ {
atomic_inc(&watch->count); refcount_inc(&watch->count);
} }
void audit_put_watch(struct audit_watch *watch) void audit_put_watch(struct audit_watch *watch)
{ {
if (atomic_dec_and_test(&watch->count)) { if (refcount_dec_and_test(&watch->count)) {
WARN_ON(watch->parent); WARN_ON(watch->parent);
WARN_ON(!list_empty(&watch->rules)); WARN_ON(!list_empty(&watch->rules));
kfree(watch->path); kfree(watch->path);
@ -178,7 +179,7 @@ static struct audit_watch *audit_init_watch(char *path)
return ERR_PTR(-ENOMEM); return ERR_PTR(-ENOMEM);
INIT_LIST_HEAD(&watch->rules); INIT_LIST_HEAD(&watch->rules);
atomic_set(&watch->count, 1); refcount_set(&watch->count, 1);
watch->path = path; watch->path = path;
watch->dev = AUDIT_DEV_UNSET; watch->dev = AUDIT_DEV_UNSET;
watch->ino = AUDIT_INO_UNSET; watch->ino = AUDIT_INO_UNSET;