It looks like attempting to write to the "store_modes" sysfs node will
run afoul of unregistered consoles:
UBSAN: array-index-out-of-bounds in drivers/video/fbdev/core/fbcon.c:122:28
index -1 is out of range for type 'fb_info *[32]'
...
fbcon_info_from_console+0x192/0x1a0 drivers/video/fbdev/core/fbcon.c:122
fbcon_new_modelist+0xbf/0x2d0 drivers/video/fbdev/core/fbcon.c:3048
fb_new_modelist+0x328/0x440 drivers/video/fbdev/core/fbmem.c:673
store_modes+0x1c9/0x3e0 drivers/video/fbdev/core/fbsysfs.c:113
dev_attr_store+0x55/0x80 drivers/base/core.c:2439
static struct fb_info *fbcon_registered_fb[FB_MAX];
...
static signed char con2fb_map[MAX_NR_CONSOLES];
...
static struct fb_info *fbcon_info_from_console(int console)
...
return fbcon_registered_fb[con2fb_map[console]];
If con2fb_map contains a -1 things go wrong here. Instead, return NULL,
as callers of fbcon_info_from_console() are trying to compare against
existing "info" pointers, so error handling should kick in correctly.
Reported-by: syzbot+a7d4444e7b6e74357...@syzkaller.appspotmail.com
Closes:
https://lore.kernel.org/all/679d0a8f.050a0220.163cdc.000c....@google.com/
Signed-off-by: Kees Cook <k...@kernel.org>
---
Cc: Simona Vetter <sim...@ffwll.ch>
Cc: Helge Deller <del...@gmx.de>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Cc: "Jiri Slaby (SUSE)" <jirisl...@kernel.org>
Cc: Javier Martinez Canillas <javi...@redhat.com>
Cc: Shixiong Ou <oushixi...@kylinos.cn>
Cc: <linux-fb...@vger.kernel.org>
Cc: <dri-devel@lists.freedesktop.org>
---
drivers/video/fbdev/core/fbcon.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index ac3c99ed92d1..2df48037688d 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -117,9 +117,14 @@ static signed char con2fb_map_boot[MAX_NR_CONSOLES];
static struct fb_info *fbcon_info_from_console(int console)
{
+ signed char fb;
WARN_CONSOLE_UNLOCKED();
- return fbcon_registered_fb[con2fb_map[console]];
+ fb = con2fb_map[console];
+ if (fb < 0 || fb >= ARRAY_SIZE(fbcon_registered_fb))
+ return NULL;
+
+ return fbcon_registered_fb[fb];
}
static int logo_lines;
--
2.34.1
