tty: vt: initialize unicode screen buffer

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: tty: vt: initialize unicode screen buffer syzbot reports kernel infoleak at vcs_read() [1], for buffer can be read immediately after resize operation. Initialize buffer using kzalloc(). ---------- #include <fcntl.h> #include <unistd.h> #include <sys/ioctl.h> #include <linux/fb.h> int main(int argc, char *argv[]) { struct fb_var_screeninfo var = { }; const int fb_fd = open("/dev/fb0", 3); ioctl(fb_fd, FBIOGET_VSCREENINFO, &var); var.yres = 0x21; ioctl(fb_fd, FBIOPUT_VSCREENINFO, &var); return read(open("/dev/vcsu", O_RDONLY), &var, sizeof(var)) == -1; } ----------

References

• https://git.kernel.org/stable/c/e02fa87e572bb7d90dcdbce9c0f519f1eb992e96
• https://git.kernel.org/stable/c/cc9e874dace0c89ae535230c7da19b764746811e
• https://git.kernel.org/stable/c/5c6c65681f39bf71bc72ed589dec3b8b20e75cac
• https://git.kernel.org/stable/c/446f123aa6021e5f75a20789f05ff3f7ae51a42f
• https://git.kernel.org/stable/c/777a462e1ae50a01fc4a871efa8e34d596a1e17d
• https://git.kernel.org/stable/c/e0ef23e9b0ad18b9fd3741b0f1ad2282e4a18def
• https://git.kernel.org/stable/c/af77c56aa35325daa2bc2bed5c2ebf169be61b86