refcount_t type and corresponding API can protect refcounters from accidental underflow and overflow and further use-after-free situations.

Signed-off-by: Xiyu Yang xiyuyang19@fudan.edu.cn Signed-off-by: Xin Tan tanxin.ctf@gmail.com --- drivers/video/fbdev/core/fbmem.c | 6 +++--- include/linux/fb.h | 3 ++- 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 98f193078c05..b7d26b928e1d 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -67,7 +67,7 @@ static struct fb_info *get_fb_info(unsigned int idx) mutex_lock(&registration_lock); fb_info = registered_fb[idx]; if (fb_info) - atomic_inc(&fb_info->count); + refcount_inc(&fb_info->count); mutex_unlock(&registration_lock);

return fb_info; @@ -75,7 +75,7 @@ static struct fb_info *get_fb_info(unsigned int idx)

static void put_fb_info(struct fb_info *fb_info) { - if (!atomic_dec_and_test(&fb_info->count)) + if (!refcount_dec_and_test(&fb_info->count)) return; if (fb_info->fbops->fb_destroy) fb_info->fbops->fb_destroy(fb_info); @@ -1594,7 +1594,7 @@ static int do_register_framebuffer(struct fb_info *fb_info) if (!registered_fb[i]) break; fb_info->node = i; - atomic_set(&fb_info->count, 1); + refcount_set(&fb_info->count, 1); mutex_init(&fb_info->lock); mutex_init(&fb_info->mm_lock);

diff --git a/include/linux/fb.h b/include/linux/fb.h index ecfbcc0553a5..5950f8f5dc74 100644 --- a/include/linux/fb.h +++ b/include/linux/fb.h @@ -2,6 +2,7 @@ #ifndef _LINUX_FB_H #define _LINUX_FB_H

+#include <linux/refcount.h> #include <linux/kgdb.h> #include <uapi/linux/fb.h>

@@ -435,7 +436,7 @@ struct fb_tile_ops {

struct fb_info { - atomic_t count; + refcount_t count; int node; int flags; /*