From 39b3cffb8cf3111738ea993e2757ab382253d86a Mon Sep 17 00:00:00 2001
From: George Kennedy <george.kennedy@oracle.com>
Date: Fri, 31 Jul 2020 12:33:11 -0400
Subject: fbcon: prevent user font height or width change from causing
potential out-of-bounds access
Git-commit: 39b3cffb8cf3111738ea993e2757ab382253d86a
Patch-mainline: v5.9-rc3
References: bsc#1112178
Add a check to fbcon_resize() to ensure that a possible change to user font
height or user font width will not allow a font data out-of-bounds access.
NOTE: must use original charcount in calculation as font charcount can
change and cannot be used to determine the font data allocated size.
Signed-off-by: George Kennedy <george.kennedy@oracle.com>
Cc: stable <stable@vger.kernel.org>
Reported-by: syzbot+38a3699c7eaf165b97a6@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/1596213192-6635-1-git-send-email-george.kennedy@oracle.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
drivers/video/console/fbcon.c | 61 ++++++++++++++++++++++++++++--------------
1 file changed, 41 insertions(+), 20 deletions(-)
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -26,7 +26,7 @@
*
* Hardware cursor support added by Emmanuel Marty (core@ggi-project.org)
* Smart redraw scrolling, arbitrary font width support, 512char font support
- * and software scrollback added by
+ * and software scrollback added by
* Jakub Jelinek (jj@ultra.linux.cz)
*
* Random hacking by Martin Mares <mj@ucw.cz>
@@ -110,7 +110,7 @@ static int softback_lines;
/* console mappings */
static int first_fb_vc;
static int last_fb_vc = MAX_NR_CONSOLES - 1;
-static int fbcon_is_default = 1;
+static int fbcon_is_default = 1;
static int fbcon_has_exited;
static int primary_device = -1;
static int fbcon_has_console_bind;
@@ -444,7 +444,7 @@ static int __init fb_console_setup(char
strlcpy(fontname, options + 5, sizeof(fontname));
continue;
}
-
+
if (!strncmp(options, "scrollback:", 11)) {
options += 11;
if (*options) {
@@ -455,7 +455,7 @@ static int __init fb_console_setup(char
}
continue;
}
-
+
if (!strncmp(options, "map:", 4)) {
options += 4;
if (*options) {
@@ -479,7 +479,7 @@ static int __init fb_console_setup(char
first_fb_vc = 0;
if (*options++ == '-')
last_fb_vc = simple_strtoul(options, &options, 10) - 1;
- fbcon_is_default = 0;
+ fbcon_is_default = 0;
continue;
}
@@ -934,7 +934,7 @@ static const char *fbcon_startup(void)
info = registered_fb[info_idx];
if (!info)
return NULL;
-
+
owner = info->fbops->owner;
if (!try_module_get(owner))
return NULL;
@@ -1425,7 +1425,7 @@ static __inline__ void ywrap_up(struct v
struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
struct fbcon_ops *ops = info->fbcon_par;
struct display *p = &fb_display[vc->vc_num];
-
+
p->yscroll += count;
if (p->yscroll >= p->vrows) /* Deal with wrap */
p->yscroll -= p->vrows;
@@ -1444,7 +1444,7 @@ static __inline__ void ywrap_down(struct
struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
struct fbcon_ops *ops = info->fbcon_par;
struct display *p = &fb_display[vc->vc_num];
-
+
p->yscroll -= count;
if (p->yscroll < 0) /* Deal with wrap */
p->yscroll += p->vrows;
@@ -1511,7 +1511,7 @@ static __inline__ void ypan_down(struct
struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
struct display *p = &fb_display[vc->vc_num];
struct fbcon_ops *ops = info->fbcon_par;
-
+
p->yscroll -= count;
if (p->yscroll < 0) {
ops->bmove(vc, info, 0, 0, p->vrows - vc->vc_rows,
@@ -2020,7 +2020,7 @@ static void fbcon_bmove(struct vc_data *
{
struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
struct display *p = &fb_display[vc->vc_num];
-
+
if (fbcon_is_inactive(vc, info))
return;
@@ -2038,7 +2038,7 @@ static void fbcon_bmove(struct vc_data *
p->vrows - p->yscroll);
}
-static void fbcon_bmove_rec(struct vc_data *vc, struct display *p, int sy, int sx,
+static void fbcon_bmove_rec(struct vc_data *vc, struct 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]];
@@ -2127,7 +2127,10 @@ static void updatescrollmode(struct disp
}
}
-static int fbcon_resize(struct vc_data *vc, unsigned int width,
+#define PITCH(w) (((w) + 7) >> 3)
+#define CALC_FONTSZ(h, p, c) ((h) * (p) * (c)) /* size = height * pitch * charcount */
+
+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]];
@@ -2136,6 +2139,24 @@ static int fbcon_resize(struct vc_data *
struct fb_var_screeninfo var = info->var;
int x_diff, y_diff, virt_w, virt_h, virt_fw, virt_fh;
+ if (ops->p && ops->p->userfont && FNTSIZE(vc->vc_font.data)) {
+ int size;
+ int pitch = PITCH(vc->vc_font.width);
+
+ /*
+ * If user font, ensure that a possible change to user font
+ * height or width will not allow a font data out-of-bounds access.
+ * NOTE: must use original charcount in calculation as font
+ * charcount can change and cannot be used to determine the
+ * font data allocated size.
+ */
+ if (pitch <= 0)
+ return -EINVAL;
+ size = CALC_FONTSZ(vc->vc_font.height, pitch, FNTCHARCNT(vc->vc_font.data));
+ if (size > FNTSIZE(vc->vc_font.data))
+ return -EINVAL;
+ }
+
virt_w = FBCON_SWAP(ops->rotate, width, height);
virt_h = FBCON_SWAP(ops->rotate, height, width);
virt_fw = FBCON_SWAP(ops->rotate, vc->vc_font.width,
@@ -2295,7 +2316,7 @@ static int fbcon_switch(struct vc_data *
ops->update_start(info);
}
- fbcon_set_palette(vc, color_table);
+ fbcon_set_palette(vc, color_table);
fbcon_clear_margins(vc, 0);
if (logo_shown == FBCON_LOGO_DRAW) {
@@ -2463,7 +2484,7 @@ static void set_vc_hi_font(struct vc_dat
vc->vc_complement_mask >>= 1;
vc->vc_s_complement_mask >>= 1;
}
-
+
/* ++Edmund: reorder the attribute bits */
if (vc->vc_can_do_color) {
unsigned short *cp =
@@ -2486,7 +2507,7 @@ static void set_vc_hi_font(struct vc_dat
vc->vc_complement_mask <<= 1;
vc->vc_s_complement_mask <<= 1;
}
-
+
/* ++Edmund: reorder the attribute bits */
{
unsigned short *cp =
@@ -2597,7 +2618,7 @@ static int fbcon_set_font(struct vc_data
int size;
int i, csum;
u8 *new_data, *data = font->data;
- int pitch = (font->width+7) >> 3;
+ int pitch = PITCH(font->width);
/* Is there a reason why fbconsole couldn't handle any charcount >256?
* If not this check should be changed to charcount < 256 */
@@ -2613,7 +2634,7 @@ static int fbcon_set_font(struct vc_data
if (fbcon_invalid_charcount(info, charcount))
return -EINVAL;
- size = h * pitch * charcount;
+ size = CALC_FONTSZ(h, pitch, charcount);
new_data = kmalloc(FONT_EXTRA_WORDS * sizeof(int) + size, GFP_USER);
@@ -2636,7 +2657,7 @@ static int fbcon_set_font(struct vc_data
/* Check if the same font is on some other console already */
for (i = first_fb_vc; i <= last_fb_vc; i++) {
struct vc_data *tmp = vc_cons[i].d;
-
+
if (fb_display[i].userfont &&
fb_display[i].fontdata &&
FNTSUM(fb_display[i].fontdata) == csum &&
@@ -2714,7 +2735,7 @@ static u16 *fbcon_screen_pos(struct vc_d
{
unsigned long p;
int line;
-
+
if (vc->vc_num != fg_console || !softback_lines)
return (u16 *) (vc->vc_origin + offset);
line = offset / vc->vc_size_row;
@@ -3671,7 +3692,7 @@ static void __exit fb_console_exit(void)
fbcon_exit();
do_unregister_con_driver(&fb_con);
console_unlock();
-}
+}
module_exit(fb_console_exit);