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From:   Daniel Vetter <daniel.vetter@ffwll.ch>
To:     DRI Development <dri-devel@lists.freedesktop.org>
Cc:     Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
        linux-fbdev@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Sam Ravnborg <sam@ravnborg.org>,
        Daniel Vetter <daniel.vetter@intel.com>,
        Helge Deller <deller@gmx.de>, Daniel Vetter <daniel@ffwll.ch>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
        Du Cheng <ducheng2@gmail.com>, Claudio Suarez <cssk@net-c.es>,
        Thomas Zimmermann <tzimmermann@suse.de>
Subject: [PATCH v2 03/19] fbcon: Introduce wrapper for console->fb_info lookup
Date:   Tue,  8 Feb 2022 22:08:08 +0100
Message-Id: <20220208210824.2238981-4-daniel.vetter@ffwll.ch>
In-Reply-To: <20220208210824.2238981-1-daniel.vetter@ffwll.ch>
References: <20220208210824.2238981-1-daniel.vetter@ffwll.ch>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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.

Acked-by: Sam Ravnborg <sam@ravnborg.org>
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 e925bb608e25..b75e638cb83d 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.  */
@@ -199,7 +211,7 @@ 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];
@@ -226,7 +238,7 @@ 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];
@@ -356,7 +368,7 @@ 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;
@@ -791,7 +803,7 @@ 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,
@@ -1014,7 +1026,7 @@ 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);
 
@@ -1392,7 +1404,7 @@ static void fbcon_set_disp(struct fb_info *info, struct fb_var_screeninfo *var,
 
 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];
 
@@ -1411,7 +1423,7 @@ 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];
 
@@ -1430,7 +1442,7 @@ 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;
 
@@ -1454,7 +1466,7 @@ 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];
 
@@ -1478,7 +1490,7 @@ 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;
 
@@ -1502,7 +1514,7 @@ 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];
 
@@ -1666,7 +1678,7 @@ static void fbcon_redraw(struct vc_data *vc, struct fbcon_display *p,
 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;
 
@@ -1708,7 +1720,7 @@ 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))
@@ -1731,7 +1743,7 @@ static void fbcon_bmove(struct vc_data *vc, int sy, int sx, int dy, int dx,
 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];
 	int scroll_partial = info->flags & FBINFO_PARTIAL_PAN_OK;
 
@@ -1996,7 +2008,7 @@ 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;
@@ -2065,7 +2077,7 @@ 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) {
@@ -2079,7 +2091,7 @@ 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
@@ -2202,7 +2214,7 @@ 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) {
@@ -2244,7 +2256,7 @@ 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;
@@ -2257,7 +2269,7 @@ 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;
@@ -2393,7 +2405,7 @@ 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;
@@ -2447,7 +2459,7 @@ 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;
@@ -2511,7 +2523,7 @@ 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)
@@ -2535,7 +2547,7 @@ 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;
 
@@ -2651,7 +2663,7 @@ 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];
@@ -2691,7 +2703,7 @@ 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)) {
@@ -2954,7 +2966,7 @@ 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)) {
@@ -2974,7 +2986,7 @@ 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;
-- 
2.34.1