s390: convert debug_info.ref_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@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>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/include/asm/debug.h b/arch/s390/include/asm/debug.h
index 0206c80..df7b54e 100644 (file)
--- a/arch/s390/include/asm/debug.h
+++ b/arch/s390/include/asm/debug.h
@@ -10,6 +10,7 @@
 #include <linux/spinlock.h>
 #include <linux/kernel.h>
 #include <linux/time.h>
+#include <linux/refcount.h>
 #include <uapi/asm/debug.h>
 
 #define DEBUG_MAX_LEVEL            6  /* debug levels range from 0 to 6 */
@@ -31,7 +32,7 @@ struct debug_view;
 typedef struct debug_info {    
        struct debug_info* next;
        struct debug_info* prev;
-       atomic_t ref_count;
+       refcount_t ref_count;
        spinlock_t lock;                        
        int level;
        int nr_areas;

diff --git a/arch/s390/kernel/debug.c b/arch/s390/kernel/debug.c
index 530226b..86b3e74 100644 (file)
--- a/arch/s390/kernel/debug.c
+++ b/arch/s390/kernel/debug.c
@@ -277,7 +277,7 @@ debug_info_alloc(const char *name, int pages_per_area, int nr_areas,
        memset(rc->views, 0, DEBUG_MAX_VIEWS * sizeof(struct debug_view *));
        memset(rc->debugfs_entries, 0 ,DEBUG_MAX_VIEWS *
                sizeof(struct dentry*));
-       atomic_set(&(rc->ref_count), 0);
+       refcount_set(&(rc->ref_count), 0);
 
        return rc;
 
@@ -361,7 +361,7 @@ debug_info_create(const char *name, int pages_per_area, int nr_areas,
         debug_area_last = rc;
         rc->next = NULL;
 
-       debug_info_get(rc);
+       refcount_set(&rc->ref_count, 1);
 out:
        return rc;
 }
@@ -416,7 +416,7 @@ static void
 debug_info_get(debug_info_t * db_info)
 {
        if (db_info)
-               atomic_inc(&db_info->ref_count);
+               refcount_inc(&db_info->ref_count);
 }
 
 /*
@@ -431,7 +431,7 @@ debug_info_put(debug_info_t *db_info)
 
        if (!db_info)
                return;
-       if (atomic_dec_and_test(&db_info->ref_count)) {
+       if (refcount_dec_and_test(&db_info->ref_count)) {
                for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
                        if (!db_info->views[i])
                                continue;