TTY: ttyprintk, don't touch behind tty->write_buf

commit ee8b593affdf893012e57f4c54a21984d1b0d92e upstream.

If a user provides a buffer larger than a tty->write_buf chunk and
passes '\r' at the end of the buffer, we touch an out-of-bound memory.

Add a check there to prevent this.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Samo Pogacnik <samo_pogacnik@t-2.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/char/ttyprintk.c b/drivers/char/ttyprintk.c
index eedd5474850c5008fe4ea957d73d5197a86dba14..59366915eee22e9ad7955ff235f09b68940661aa 100644 (file)
--- a/drivers/char/ttyprintk.c
+++ b/drivers/char/ttyprintk.c
@@ -67,7 +67,7 @@ static int tpk_printk(const unsigned char *buf, int count)
                                tmp[tpk_curr + 1] = '\0';
                                printk(KERN_INFO "%s%s", tpk_tag, tmp);
                                tpk_curr = 0;
-                               if (buf[i + 1] == '\n')
+                               if ((i + 1) < count && buf[i + 1] == '\n')
                                        i++;
                                break;
                        case '\n':