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CVE-2024-50048

Estado: ModificadaMedia (5.5)—

In the Linux kernel, the following vulnerability has been resolved:

fbcon: Fix a NULL pointer dereference issue in fbcon_putcs

syzbot has found a NULL pointer dereference bug in fbcon. Here is the simplified C reproducer:

After calling ioctl(fd1, TIOCLINUX, &param), the subsequent ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb) causes the kernel to follow a different execution path:

Since ops->putcs is a NULL pointer, this leads to a kernel panic. To prevent this, we need to call set_blitting_type() within set_con2fb_map() to properly initialize ops->putcs.

Detalles técnicos trazas, registros y código del informe original
struct param {
	uint8_t type;
	struct tiocl_selection ts;
};

int main()
{
	struct fb_con2fbmap con2fb;
	struct param param;

	int fd = open("/dev/fb1", 0, 0);

	con2fb.console = 0x19;
	con2fb.framebuffer = 0;
	ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb);

	param.type = 2;
	param.ts.xs = 0; param.ts.ys = 0;
	param.ts.xe = 0; param.ts.ye = 0;
	param.ts.sel_mode = 0;

	int fd1 = open("/dev/tty1", O_RDWR, 0);
	ioctl(fd1, TIOCLINUX, &param);

	con2fb.console = 1;
	con2fb.framebuffer = 0;
	ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb);

	return 0;
}

 set_con2fb_map
  -> con2fb_init_display
   -> fbcon_set_disp
    -> redraw_screen
     -> hide_cursor
      -> clear_selection
       -> highlight
        -> invert_screen
         -> do_update_region
          -> fbcon_putcs
           -> ops->putcs

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

Mostrar
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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfbcon: Fix a NULL pointer dereference issue in fbcon_putcs\n\nsyzbot has found a NULL pointer dereference bug in fbcon.\nHere is the simplified C reproducer:\n\nstruct param {\n\tuint8_t type;\n\tstruct tiocl_selection ts;\n};\n\nint main()\n{\n\tstruct fb_con2fbmap con2fb;\n\tstruct param param;\n\n\tint fd = open(\"/dev/fb1\", 0, 0);\n\n\tcon2fb.console = 0x19;\n\tcon2fb.framebuffer = 0;\n\tioctl(fd, FBIOPUT_CON2FBMAP, &con2fb);\n\n\tparam.type = 2;\n\tparam.ts.xs = 0; param.ts.ys = 0;\n\tparam.ts.xe = 0; param.ts.ye = 0;\n\tparam.ts.sel_mode = 0;\n\n\tint fd1 = open(\"/dev/tty1\", O_RDWR, 0);\n\tioctl(fd1, TIOCLINUX, &param);\n\n\tcon2fb.console = 1;\n\tcon2fb.framebuffer = 0;\n\tioctl(fd, FBIOPUT_CON2FBMAP, &con2fb);\n\n\treturn 0;\n}\n\nAfter calling ioctl(fd1, TIOCLINUX, &param), the subsequent ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb)\ncauses the kernel to follow a different execution path:\n\n set_con2fb_map\n  -> con2fb_init_display\n   -> fbcon_set_disp\n    -> redraw_screen\n     -> hide_cursor\n      -> clear_selection\n       -> highlight\n        -> invert_screen\n         -> do_update_region\n          -> fbcon_putcs\n           -> ops->putcs\n\nSince ops->putcs is a NULL pointer, this leads to a kernel panic.\nTo prevent this, we need to call set_blitting_type() within set_con2fb_map()\nto properly initialize ops->putcs."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: fbcon: soluciona un problema de desreferencia de puntero NULL en fbcon_putcs syzbot ha encontrado un error de desreferencia de puntero NULL en fbcon. Aquí está el reproductor C simplificado: struct param { uint8_t type; struct tiocl_selection ts; }; int main() { struct fb_con2fbmap con2fb; struct param param; int fd = open(\"/dev/fb1\", 0, 0); con2fb.console = 0x19; con2fb.framebuffer = 0; ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb); param.type = 2; param.ts.xs = 0; param.ts.ys = 0; param.ts.xe = 0; param.ts.ye = 0; param.ts.sel_mode = 0; int fd1 = open(\"/dev/tty1\", O_RDWR, 0); ioctl(fd1, TIOCLINUX, &param); con2fb.console = 1; con2fb.framebuffer = 0; ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb); devolver 0; } Después de llamar a ioctl(fd1, TIOCLINUX, &param), el ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb) subsiguiente hace que el núcleo siga una ruta de ejecución diferente: set_con2fb_map -> con2fb_init_display -> fbcon_set_disp -> redraw_screen -> hide_cursor -> clear_selection -> highlight -> invert_screen -> do_update_region -> fbcon_putcs -> ops->putcs Dado que ops->putcs es un puntero NULL, esto lleva a un pánico del núcleo. Para evitar esto, necesitamos llamar a set_blitting_type() dentro de set_con2fb_map() para inicializar correctamente ops->putcs."
    }
  ],
  "lastModified": "2026-06-17T08:03:27.597",
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