tty: wipe buffer if not echoing data

commit b97b3d9fb57860a60592859e332de7759fd54c2e upstream.

If we are not echoing the data to userspace or the console is in icanon
mode, then perhaps it is a "secret" so we should wipe it once we are
done with it.

This mirrors the logic that the audit code has.

Reported-by: aszlig <aszlig@nix.build>
Tested-by: Milan Broz <gmazyland@gmail.com>
Tested-by: Daniel Zatovic <daniel.zatovic@gmail.com>
Tested-by: aszlig <aszlig@nix.build>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index f53682b..4d46a1c 100644 (file)
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -188,15 +188,29 @@ static int receive_room(struct tty_struct *tty)
        return left;
 }
 
+/* If we are not echoing the data, perhaps this is a secret so erase it */
+static inline void zero_buffer(struct tty_struct *tty, u8 *buffer, int size)
+{
+       bool icanon = !!L_ICANON(tty);
+       bool no_echo = !L_ECHO(tty);
+
+       if (icanon && no_echo)
+               memset(buffer, 0x00, size);
+}
+
 static inline int tty_copy_to_user(struct tty_struct *tty,
                                        void __user *to,
-                                       const void *from,
+                                       void *from,
                                        unsigned long n)
 {
        struct n_tty_data *ldata = tty->disc_data;
+       int retval;
 
        tty_audit_add_data(tty, from, n, ldata->icanon);
-       return copy_to_user(to, from, n);
+       retval = copy_to_user(to, from, n);
+       if (!retval)
+               zero_buffer(tty, from, n);
+       return retval;
 }
 
 /**
@@ -2006,6 +2020,7 @@ static int copy_from_read_buf(struct tty_struct *tty,
                is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
                tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
                                ldata->icanon);
+               zero_buffer(tty, read_buf_addr(ldata, tail), n);
                ldata->read_tail += n;
                /* Turn single EOF into zero-length read */
                if (L_EXTPROC(tty) && ldata->icanon && is_eof && !read_cnt(ldata))