On Thu, Jun 02, 2022 at 10:06:28PM +0200, Helge Deller wrote:

The user may use the fbcon=vc:<n1>-<n2> option to tell fbcon to take over the given range (n1...n2) of consoles. The value for n1 and n2 needs to be a positive number and up to (MAX_NR_CONSOLES - 1). The given values were not fully checked against those boundaries yet.

To fix the issue, convert first_fb_vc and last_fb_vc to unsigned integers and check them against the upper boundary, and make sure that first_fb_vc is smaller than last_fb_vc.

Signed-off-by: Helge Deller deller@gmx.de Cc: stable@vger.kernel.org

Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 2fc1b80a26ad..c2f9e5711c39 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -115,8 +115,8 @@ static int logo_lines; enums. */ static int logo_shown = FBCON_LOGO_CANSHOW; /* console mappings */ -static int first_fb_vc; -static int last_fb_vc = MAX_NR_CONSOLES - 1; +static unsigned int first_fb_vc; +static unsigned int last_fb_vc = MAX_NR_CONSOLES - 1; static int fbcon_is_default = 1; static int primary_device = -1; static int fbcon_has_console_bind; @@ -464,10 +464,12 @@ static int __init fb_console_setup(char *this_opt) options += 3; if (*options) first_fb_vc = simple_strtoul(options, &options, 10) - 1;

• 	if (first_fb_vc < 0)
  

• 	if (first_fb_vc >= MAX_NR_CONSOLES)
  	first_fb_vc = 0;
  if (*options++ == '-')
  	last_fb_vc = simple_strtoul(options, &options, 10) - 1;
  

• 	if (last_fb_vc < first_fb_vc || last_fb_vc >= MAX_NR_CONSOLES)
  

• 		last_fb_vc = MAX_NR_CONSOLES - 1;
  fbcon_is_default = 0;
  continue;
  

  }