[PATCH] fbcon: Fix a NULL pointer dereference issue in fbcon_putcs

[Qianqiang Liu]

Hi, 

I simplified the C reproducer as follows:

#include <stdint.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <linux/tiocl.h>
#include <sys/ioctl.h>

struct param {
        uint8_t type;
        struct tiocl_selection ts;
};

int main()
{
        write(1, "executing program\n", sizeof("executing program\n") - 1);

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

        struct fb_con2fbmap con2fb;
        con2fb.console = 0x19;
        con2fb.framebuffer = 0;
        ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb);

        int fd1 = open("/dev/tty1", O_RDWR, 0);

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

        ioctl(fd1, TIOCLINUX, &param);

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

        return 0;
}

But I still need time to debug the kernel code..

-- 
Best,
Qianqiang Liu