tty: fix compat TIOCGSERIAL leaking uninitialized memory
authorEric Biggers <ebiggers@google.com>
Mon, 24 Feb 2020 18:20:43 +0000 (10:20 -0800)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 18 Mar 2020 12:15:13 +0000 (13:15 +0100)
Commit 77654350306a ("take compat TIOC[SG]SERIAL treatment into
tty_compat_ioctl()") changed the compat version of TIOCGSERIAL to start
copying a whole 'serial_struct32' to userspace rather than individual
fields, but failed to initialize all padding and fields -- namely the
hole after the 'iomem_reg_shift' field, and the 'reserved' field.

Fix this by initializing the struct to zero.

[v2: use sizeof, and convert the adjacent line for consistency.]

Reported-by: syzbot+8da9175e28eadcb203ce@syzkaller.appspotmail.com
Fixes: 77654350306a ("take compat TIOC[SG]SERIAL treatment into tty_compat_ioctl()")
Cc: <stable@vger.kernel.org> # v4.20+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200224182044.234553-2-ebiggers@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/tty/tty_io.c

index 1fcf7ad..db4a13b 100644 (file)
@@ -2730,7 +2730,9 @@ static int compat_tty_tiocgserial(struct tty_struct *tty,
        struct serial_struct32 v32;
        struct serial_struct v;
        int err;
        struct serial_struct32 v32;
        struct serial_struct v;
        int err;
-       memset(&v, 0, sizeof(struct serial_struct));
+
+       memset(&v, 0, sizeof(v));
+       memset(&v32, 0, sizeof(v32));
 
        if (!tty->ops->set_serial)
                return -ENOTTY;
 
        if (!tty->ops->set_serial)
                return -ENOTTY;