Bug 209078

There is a memory leak in the `vidcontrol` utility in the `load_vt4font`:

usr.sbin/vidcontrol/vidcontrol.c:

static int
load_vt4font(FILE *f)
{
	struct vt4font_header fh;
	static vfnt_t vfnt;
	size_t glyphsize;
	unsigned int i;

	if (fread(&fh, sizeof fh, 1, f) != 1) {
		perror("file_header");
		return (1);
	}

	if (memcmp(fh.magic, "VFNT0002", 8) != 0) {
		fprintf(stderr, "Bad magic\n");
		return (1);
	}

	for (i = 0; i < VFNT_MAPS; i++)
		vfnt.map_count[i] = be32toh(fh.map_count[i]);
	vfnt.glyph_count = be32toh(fh.glyph_count);
	vfnt.width = fh.width;
	vfnt.height = fh.height;

	glyphsize = howmany(vfnt.width, 8) * vfnt.height * vfnt.glyph_count;
	vfnt.glyphs = malloc(glyphsize);

	if (fread(vfnt.glyphs, glyphsize, 1, f) != 1) {
		perror("glyphs");
		return (1);
	}

	for (i = 0; i < VFNT_MAPS; i++)
		vfnt.map[i] = load_vt4mappingtable(vfnt.map_count[i], f);

	if (ioctl(STDIN_FILENO, PIO_VFONT, &vfnt) == -1) {
		perror("PIO_VFONT");
		return (1);
	}
	return (0);
}

After the `vfnt.glyphs` buffer has been allocated with `malloc`, the function can return without freeing the buffer if `fread` or `ioctl` fail.

This is only a minor bug, since the process exits almost immediately after calling this function anyway, but I would like to `free` the buffer as a matter of code correctness.

This function also doesn't check the return result of `malloc`, which could lead to writing to `NULL` if the allocation fails.

My proposal is to add the following lines to this function:

	vfnt.glyphs = malloc(glyphsize);
+	if (vfnt.glyphs == NULL) {
+		perror("malloc");
+		return (1);
+	}

	if (fread(vfnt.glyphs, glyphsize, 1, f) != 1) {
		perror("glyphs");
+		free(vfnt.glyphs);
		return (1);
	}

	for (i = 0; i < VFNT_MAPS; i++)
		vfnt.map[i] = load_vt4mappingtable(vfnt.map_count[i], f);

	if (ioctl(STDIN_FILENO, PIO_VFONT, &vfnt) == -1) {
		perror("PIO_VFONT");
+		free(vfnt.glyphs);
		return (1);
	}