linux-kernel - Re: [PATCH] fbcon: Add check for return value

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <04969c5e-c04f-43d6-abe0-e458df89dca6@gmx.de>
Date: Tue, 30 Dec 2025 10:27:08 +0100
From: Helge Deller <deller@....de>
To: Ваторопин Андрей
 <a.vatoropin@...t.ru>
Cc: "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
 "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "lvc-project@...uxtesting.org" <lvc-project@...uxtesting.org>
Subject: Re: [PATCH] fbcon: Add check for return value

On 12/17/25 10:11, ÐÐ°ÑÐ¾ÑÐ¾Ð¿Ð¸Ð½ ÐÐ½Ð´ÑÐµÐ¹ wrote:
> From: Andrey Vatoropin <a.vatoropin@...t.ru>
> 
> If fbcon_open() fails when called from con2fb_acquire_newinfo() then
> info->fbcon_par pointer remains NULL which is later dereferenced.
> 
> Add check for return value of the function con2fb_acquire_newinfo() to
> avoid it.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.

I was unsure if I should apply this patch since we don't have a real problem.

This is inside the fbcon_init() function, so if con2fb_acquire_newinfo()
ever would have returned NULL, the kernel would have crashed and someone
would have reported it (or will report in the future if it happens).

Nevertheless, for correctness, I was tempted to change the check to a
WARN_ON() or BUG_ON() instead, but again: it never happened, so why
add bloat to the kernel ?

In the end, I've now applied this patch to the linux-fbdev git tree
as-is, just to avoid other people send similar patches based on
verification tool reports...

Thanks!
Helge
  
> Fixes: d1baa4ffa677 ("fbcon: set_con2fb_map fixes")
> Cc: stable@...r.kernel.org
> Signed-off-by: Andrey Vatoropin <a.vatoropin@...t.ru>
> ---
>   drivers/video/fbdev/core/fbcon.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> index e7e07eb2142e..7453377f3433 100644
> --- a/drivers/video/fbdev/core/fbcon.c
> +++ b/drivers/video/fbdev/core/fbcon.c
> @@ -1047,7 +1047,8 @@ static void fbcon_init(struct vc_data *vc, bool init)
>   		return;
>   
>   	if (!info->fbcon_par)
> -		con2fb_acquire_newinfo(vc, info, vc->vc_num);
> +		if (con2fb_acquire_newinfo(vc, info, vc->vc_num))
> +			return;
>   
>   	/* If we are not the first console on this
>   	   fb, copy the font from that console */