[PATCH] fbcon: Initialize ops->info early

[PATCH] fbcon: Initialize ops->info early

[Thierry Reding]

From: Thierry Reding <treding@nvidia.com>

During console takeover, which happens for all DRM/KMS setups using the
fbdev helpers, fbcon_startup() is called before fbcon_init() and as a
result con2fb_acquire_newinfo() will not be called (info->fbcon_par was
set to non-NULL in fbcon_startup()) to assign ops->info.

This causes the cursor_timer_handler() to unreference a NULL pointer.

Avoid this by unconditionally assigning ops->info during fbcon_startup()
so that it will be available early, but keep the additional assignment
in con2fb_acquire_newinfo() to support console remapping at runtime.

Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
---
 drivers/video/fbdev/core/fbcon.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 3b4a96379128..929ca472c524 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -962,6 +962,7 @@ static const char *fbcon_startup(void)
 	ops->graphics = 1;
 	ops->cur_rotate = -1;
 	ops->cur_blink_jiffies = HZ / 5;
+	ops->info = info;
 	info->fbcon_par = ops;
 	if (initial_rotation != -1)
 		p->con_rotate = initial_rotation;
-- 
2.14.1

Re: [PATCH] fbcon: Initialize ops->info early

[Bartlomiej Zolnierkiewicz]

On Monday, November 13, 2017 10:45:46 AM Thierry Reding wrote:
> From: Thierry Reding <treding@nvidia.com>
> 
> During console takeover, which happens for all DRM/KMS setups using the
> fbdev helpers, fbcon_startup() is called before fbcon_init() and as a
> result con2fb_acquire_newinfo() will not be called (info->fbcon_par was
> set to non-NULL in fbcon_startup()) to assign ops->info.
> 
> This causes the cursor_timer_handler() to unreference a NULL pointer.
> 
> Avoid this by unconditionally assigning ops->info during fbcon_startup()
> so that it will be available early, but keep the additional assignment
> in con2fb_acquire_newinfo() to support console remapping at runtime.
> 
> Cc: Kees Cook <keescook@chromium.org>
> Signed-off-by: Thierry Reding <treding@nvidia.com>

Patch queued for 4.15, thanks.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics