speakup: Avoid crash on very long word

In case a console is set up really large and contains a really long word
(> 256 characters), we have to stop before the length of the word buffer.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Fixes: c6e3fd2 ("Staging: add speakup to the staging directory")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240323164843.1426997-1-samuel.thibault@ens-lyon.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: sthibaul

drivers/accessibility/speakup/main.c

@@ -574,7 +574,7 @@ static u_long get_word(struct vc_data *vc)
 	}
 	attr_ch = get_char(vc, (u_short *)tmp_pos, &spk_attr);
 	buf[cnt++] = attr_ch;
-	while (tmpx < vc->vc_cols - 1) {
+	while (tmpx < vc->vc_cols - 1 && cnt < sizeof(buf) - 1) {
 		tmp_pos += 2;
 		tmpx++;
 		ch = get_char(vc, (u_short *)tmp_pos, &temp);