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fbmem: Convert from atomic_t to refcount_t on fb_info->count

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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>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1626674392-55857-1-git-send-email-xiyuyang19@fudan.edu.cn
This commit is contained in:
Xiyu Yang 2021-07-19 13:59:45 +08:00 committed by Sam Ravnborg
parent 98a6543917
commit 0189cb57b9
2 changed files with 5 additions and 4 deletions
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6
drivers/video/fbdev/core/fbmem.c
View File

@ -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);
@ -1590,7 +1590,7 @@ 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);

3
include/linux/fb.h
View File

@ -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;
/*