[PATCH AUTOSEL 6.0 32/39] fbcon: Use kzalloc() in fbcon_prepare_logo()

Sasha Levin
2022-11-28T17:41:57Z

From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

[ Upstream commit a6a00d7e8ffd78d1cdb7a43f1278f081038c638f ]

A kernel built with syzbot's config file reported that

scr_memcpyw(q, save, array3_size(logo_lines, new_cols, 2))

causes uninitialized "save" to be copied.

----------
[drm] Initialized vgem 1.0.0 20120112 for vgem on minor 0
[drm] Initialized vkms 1.0.0 20180514 for vkms on minor 1
Console: switching to colour frame buffer device 128x48
=====================================================
BUG: KMSAN: uninit-value in do_update_region+0x4b8/0xba0
do_update_region+0x4b8/0xba0
update_region+0x40d/0x840
fbcon_switch+0x3364/0x35e0
redraw_screen+0xae3/0x18a0
do_bind_con_driver+0x1cb3/0x1df0
do_take_over_console+0x11cb/0x13f0
fbcon_fb_registered+0xacc/0xfd0
register_framebuffer+0x1179/0x1320
__drm_fb_helper_initial_config_and_unlock+0x23ad/0x2b40
drm_fbdev_client_hotplug+0xbea/0xda0
drm_fbdev_generic_setup+0x65e/0x9d0
vkms_init+0x9f3/0xc76
(...snipped...)

Uninit was stored to memory at:
fbcon_prepare_logo+0x143b/0x1940
fbcon_init+0x2c1b/0x31c0
visual_init+0x3e7/0x820
do_bind_con_driver+0x14a4/0x1df0
do_take_over_console+0x11cb/0x13f0
fbcon_fb_registered+0xacc/0xfd0
register_framebuffer+0x1179/0x1320
__drm_fb_helper_initial_config_and_unlock+0x23ad/0x2b40
drm_fbdev_client_hotplug+0xbea/0xda0
drm_fbdev_generic_setup+0x65e/0x9d0
vkms_init+0x9f3/0xc76
(...snipped...)

Uninit was created at:
__kmem_cache_alloc_node+0xb69/0x1020
__kmalloc+0x379/0x680
fbcon_prepare_logo+0x704/0x1940
fbcon_init+0x2c1b/0x31c0
visual_init+0x3e7/0x820
do_bind_con_driver+0x14a4/0x1df0
do_take_over_console+0x11cb/0x13f0
fbcon_fb_registered+0xacc/0xfd0
register_framebuffer+0x1179/0x1320
__drm_fb_helper_initial_config_and_unlock+0x23ad/0x2b40
drm_fbdev_client_hotplug+0xbea/0xda0
drm_fbdev_generic_setup+0x65e/0x9d0
vkms_init+0x9f3/0xc76
(...snipped...)

CPU: 2 PID: 1 Comm: swapper/0 Not tainted 6.1.0-rc4-00356-g8f2975c2bb4c #924
Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
----------

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/cad03d25-0ea0-32c4-8173-fd1895314bce@I-love.SAKURA.ne.jp
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/video/fbdev/core/fbcon.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 098b62f7b701..c0143d38df83 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -577,7 +577,7 @@ static void fbcon_prepare_logo(struct vc_data *vc, struct fb_info *info,
if (scr_readw(r) != vc->vc_video_erase_char)
break;
if (r != q && new_rows >= rows + logo_lines) {
- save = kmalloc(array3_size(logo_lines, new_cols, 2),
+ save = kzalloc(array3_size(logo_lines, new_cols, 2),
GFP_KERNEL);
if (save) {
int i = min(cols, new_cols);
--
2.35.1