[PATCH 05/21] fbcon: Introduce wrapper for console->fb_info lookup

Daniel Vetter
2022-01-31T21:06:56Z

Half of it is protected by console_lock, but the other half is a lot
more awkward: Registration/deregistration of fbdev are serialized, but
we don't really clear out anything in con2fb_map and so there's
potential for use-after free mixups.

First step is to encapsulate the lookup.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Du Cheng <ducheng2@gmail.com>
Cc: Claudio Suarez <cssk@net-c.es>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
---
drivers/video/fbdev/core/fbcon.c | 76 ++++++++++++++++++--------------
1 file changed, 44 insertions(+), 32 deletions(-)

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 2a575620ef59..8f971de35885 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -110,6 +110,18 @@ static struct fbcon_display fb_display[MAX_NR_CONSOLES];
static signed char con2fb_map[MAX_NR_CONSOLES];
static signed char con2fb_map_boot[MAX_NR_CONSOLES];

+static struct fb_info *fbcon_info_from_console(int console)
+{
+ WARN_CONSOLE_UNLOCKED();
+
+ /*
+ * Note that only con2fb_map is protected by the console lock,
+ * registered_fb is protected by a separate mutex. This lookup can
+ * therefore race.
+ */
+ return registered_fb[con2fb_map[console]];
+}
+
static int logo_lines;
/* logo_shown is an index to vc_cons when >= 0; otherwise follows FBCON_LOGO
enums. */
@@ -197,7 +209,7 @@ static void fbcon_rotate(struct fb_info *info, u32 rotate)
if (!ops || ops->currcon == -1)
return;

- fb_info = registered_fb[con2fb_map[ops->currcon]];
+ fb_info = fbcon_info_from_console(ops->currcon);

if (info == fb_info) {
struct fbcon_display *p = &fb_display[ops->currcon];
@@ -224,7 +236,7 @@ static void fbcon_rotate_all(struct fb_info *info, u32 rotate)
for (i = first_fb_vc; i <= last_fb_vc; i++) {
vc = vc_cons[i].d;
if (!vc || vc->vc_mode != KD_TEXT ||
- registered_fb[con2fb_map[i]] != info)
+ fbcon_info_from_console(i) != info)
continue;

p = &fb_display[vc->vc_num];
@@ -354,7 +366,7 @@ static void fb_flashcursor(struct work_struct *work)
vc = vc_cons[ops->currcon].d;

if (!vc || !con_is_visible(vc) ||
- registered_fb[con2fb_map[vc->vc_num]] != info ||
+ fbcon_info_from_console(vc->vc_num) != info ||
vc->vc_deccm != 1) {
console_unlock();
return;
@@ -789,7 +801,7 @@ static void con2fb_init_display(struct vc_data *vc, struct fb_info *info,
if (show_logo) {
struct vc_data *fg_vc = vc_cons[fg_console].d;
struct fb_info *fg_info =
- registered_fb[con2fb_map[fg_console]];
+ fbcon_info_from_console(fg_console);

fbcon_prepare_logo(fg_vc, fg_info, fg_vc->vc_cols,
fg_vc->vc_rows, fg_vc->vc_cols,
@@ -1012,7 +1024,7 @@ static void fbcon_init(struct vc_data *vc, int init)
if (con2fb_map[vc->vc_num] == -1)
con2fb_map[vc->vc_num] = info_idx;

- info = registered_fb[con2fb_map[vc->vc_num]];
+ info = fbcon_info_from_console(vc->vc_num);

if (logo_shown < 0 && console_loglevel <= CONSOLE_LOGLEVEL_QUIET)
logo_shown = FBCON_LOGO_DONTSHOW;
@@ -1231,7 +1243,7 @@ static void fbcon_deinit(struct vc_data *vc)
static void fbcon_clear(struct vc_data *vc, int sy, int sx, int height,
int width)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_ops *ops = info->fbcon_par;

struct fbcon_display *p = &fb_display[vc->vc_num];
@@ -1269,7 +1281,7 @@ static void fbcon_clear(struct vc_data *vc, int sy, int sx, int height,
static void fbcon_putcs(struct vc_data *vc, const unsigned short *s,
int count, int ypos, int xpos)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_display *p = &fb_display[vc->vc_num];
struct fbcon_ops *ops = info->fbcon_par;

@@ -1289,7 +1301,7 @@ static void fbcon_putc(struct vc_data *vc, int c, int ypos, int xpos)

static void fbcon_clear_margins(struct vc_data *vc, int bottom_only)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_ops *ops = info->fbcon_par;

if (!fbcon_is_inactive(vc, info))
@@ -1298,7 +1310,7 @@ static void fbcon_clear_margins(struct vc_data *vc, int bottom_only)

static void fbcon_cursor(struct vc_data *vc, int mode)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_ops *ops = info->fbcon_par;
int c = scr_readw((u16 *) vc->vc_pos);

@@ -1427,7 +1439,7 @@ static void fbcon_redraw_move(struct vc_data *vc, struct fbcon_display *p,

static __inline__ void ywrap_up(struct vc_data *vc, int count)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_ops *ops = info->fbcon_par;
struct fbcon_display *p = &fb_display[vc->vc_num];

@@ -1446,7 +1458,7 @@ static __inline__ void ywrap_up(struct vc_data *vc, int count)

static __inline__ void ywrap_down(struct vc_data *vc, int count)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_ops *ops = info->fbcon_par;
struct fbcon_display *p = &fb_display[vc->vc_num];

@@ -1465,7 +1477,7 @@ static __inline__ void ywrap_down(struct vc_data *vc, int count)

static __inline__ void ypan_up(struct vc_data *vc, int count)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_display *p = &fb_display[vc->vc_num];
struct fbcon_ops *ops = info->fbcon_par;

@@ -1489,7 +1501,7 @@ static __inline__ void ypan_up(struct vc_data *vc, int count)

static __inline__ void ypan_up_redraw(struct vc_data *vc, int t, int count)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_ops *ops = info->fbcon_par;
struct fbcon_display *p = &fb_display[vc->vc_num];

@@ -1513,7 +1525,7 @@ static __inline__ void ypan_up_redraw(struct vc_data *vc, int t, int count)

static __inline__ void ypan_down(struct vc_data *vc, int count)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_display *p = &fb_display[vc->vc_num];
struct fbcon_ops *ops = info->fbcon_par;

@@ -1537,7 +1549,7 @@ static __inline__ void ypan_down(struct vc_data *vc, int count)

static __inline__ void ypan_down_redraw(struct vc_data *vc, int t, int count)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_ops *ops = info->fbcon_par;
struct fbcon_display *p = &fb_display[vc->vc_num];

@@ -1562,7 +1574,7 @@ static __inline__ void ypan_down_redraw(struct vc_data *vc, int t, int count)
static void fbcon_bmove_rec(struct vc_data *vc, struct fbcon_display *p, int sy, int sx,
int dy, int dx, int height, int width, u_int y_break)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_ops *ops = info->fbcon_par;
u_int b;

@@ -1604,7 +1616,7 @@ static void fbcon_bmove_rec(struct vc_data *vc, struct fbcon_display *p, int sy,
static void fbcon_bmove(struct vc_data *vc, int sy, int sx, int dy, int dx,
int height, int width)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_display *p = &fb_display[vc->vc_num];

if (fbcon_is_inactive(vc, info))
@@ -1733,7 +1745,7 @@ static void fbcon_redraw(struct vc_data *vc, struct fbcon_display *p,
static bool fbcon_scroll(struct vc_data *vc, unsigned int t, unsigned int b,
enum con_scroll dir, unsigned int count)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_display *p = &fb_display[vc->vc_num];
#ifdef CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION
int scroll_partial = info->flags & FBINFO_PARTIAL_PAN_OK;
@@ -2013,7 +2025,7 @@ static void updatescrollmode(struct fbcon_display *p,
static int fbcon_resize(struct vc_data *vc, unsigned int width,
unsigned int height, unsigned int user)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_ops *ops = info->fbcon_par;
struct fbcon_display *p = &fb_display[vc->vc_num];
struct fb_var_screeninfo var = info->var;
@@ -2082,7 +2094,7 @@ static int fbcon_switch(struct vc_data *vc)
struct fb_var_screeninfo var;
int i, ret, prev_console;

- info = registered_fb[con2fb_map[vc->vc_num]];
+ info = fbcon_info_from_console(vc->vc_num);
ops = info->fbcon_par;

if (logo_shown >= 0) {
@@ -2096,7 +2108,7 @@ static int fbcon_switch(struct vc_data *vc)

prev_console = ops->currcon;
if (prev_console != -1)
- old_info = registered_fb[con2fb_map[prev_console]];
+ old_info = fbcon_info_from_console(prev_console);
/*
* FIXME: If we have multiple fbdev's loaded, we need to
* update all info->currcon. Perhaps, we can place this
@@ -2219,7 +2231,7 @@ static void fbcon_generic_blank(struct vc_data *vc, struct fb_info *info,

static int fbcon_blank(struct vc_data *vc, int blank, int mode_switch)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_ops *ops = info->fbcon_par;

if (mode_switch) {
@@ -2261,7 +2273,7 @@ static int fbcon_blank(struct vc_data *vc, int blank, int mode_switch)

static int fbcon_debug_enter(struct vc_data *vc)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_ops *ops = info->fbcon_par;

ops->save_graphics = ops->graphics;
@@ -2274,7 +2286,7 @@ static int fbcon_debug_enter(struct vc_data *vc)

static int fbcon_debug_leave(struct vc_data *vc)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_ops *ops = info->fbcon_par;

ops->graphics = ops->save_graphics;
@@ -2410,7 +2422,7 @@ static void set_vc_hi_font(struct vc_data *vc, bool set)
static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount,
const u8 * data, int userfont)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_ops *ops = info->fbcon_par;
struct fbcon_display *p = &fb_display[vc->vc_num];
int resize;
@@ -2464,7 +2476,7 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount,
static int fbcon_set_font(struct vc_data *vc, struct console_font *font,
unsigned int flags)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
unsigned charcount = font->charcount;
int w = font->width;
int h = font->height;
@@ -2528,7 +2540,7 @@ static int fbcon_set_font(struct vc_data *vc, struct console_font *font,

static int fbcon_set_def_font(struct vc_data *vc, struct console_font *font, char *name)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
const struct font_desc *f;

if (!name)
@@ -2552,7 +2564,7 @@ static struct fb_cmap palette_cmap = {

static void fbcon_set_palette(struct vc_data *vc, const unsigned char *table)
{
- struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+ struct fb_info *info = fbcon_info_from_console(vc->vc_num);
int i, j, k, depth;
u8 val;

@@ -2668,7 +2680,7 @@ static void fbcon_modechanged(struct fb_info *info)
return;
vc = vc_cons[ops->currcon].d;
if (vc->vc_mode != KD_TEXT ||
- registered_fb[con2fb_map[ops->currcon]] != info)
+ fbcon_info_from_console(ops->currcon) != info)
return;

p = &fb_display[vc->vc_num];
@@ -2708,7 +2720,7 @@ static void fbcon_set_all_vcs(struct fb_info *info)
for (i = first_fb_vc; i <= last_fb_vc; i++) {
vc = vc_cons[i].d;
if (!vc || vc->vc_mode != KD_TEXT ||
- registered_fb[con2fb_map[i]] != info)
+ fbcon_info_from_console(i) != info)
continue;

if (con_is_visible(vc)) {
@@ -2971,7 +2983,7 @@ void fbcon_fb_blanked(struct fb_info *info, int blank)

vc = vc_cons[ops->currcon].d;
if (vc->vc_mode != KD_TEXT ||
- registered_fb[con2fb_map[ops->currcon]] != info)
+ fbcon_info_from_console(ops->currcon) != info)
return;

if (con_is_visible(vc)) {
@@ -2991,7 +3003,7 @@ void fbcon_new_modelist(struct fb_info *info)
const struct fb_videomode *mode;

for (i = first_fb_vc; i <= last_fb_vc; i++) {
- if (registered_fb[con2fb_map[i]] != info)
+ if (fbcon_info_from_console(i) != info)
continue;
if (!fb_display[i].mode)
continue;
--
2.33.0