[PATCH v2] tty: rocket: Fix a kernel address leak in rp_ioctl

[Fuqian Huang]

If the cmd is RCPK_GET_STRUCT, copy_to_user will copy
info to user space. As info->port.ops is the address of
a constant object rocket_port_ops (assigned in init_r_port),
a kernel address leakage happens.

This patch sets all the pointer fields to NULL before copy the
object to user space to avoid kernel address leakage.

Signed-off-by: Fuqian Huang <huangfq.dax...@gmail.com>
---
 drivers/tty/rocket.c | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/rocket.c b/drivers/tty/rocket.c
index b121d8f8f3d7..a7bcf44b61bd 100644
--- a/drivers/tty/rocket.c
+++ b/drivers/tty/rocket.c
@@ -1271,6 +1271,34 @@ static int get_version(struct r_port *info, struct 
rocket_version __user *retver
        return 0;
 }
 
+static int get_struct(struct r_port *info, void *argp)
+{
+       struct r_port *new;
+       int ret = 0;
+
+       new = kzalloc(sizeof (struct r_port), GFP_KERNEL);
+       if (!new)
+               return -ENOMEM;
+       memcpy(new, info, sizeof (struct r_port));
+       new->port.tty = NULL;
+       new->port.itty = NULL;
+       new->port.ops = NULL;
+       new->port.client_ops = NULL;
+       memset(&new->port.open_wait.head, 0, sizeof (struct list_head));
+       memset(&new->port.delta_msr_wait.head, 0, sizeof (struct list_head));
+       memset(&new->port.mutex.wait_list, 0, sizeof (struct list_head));
+       memset(&new->port.buf_mutex.wait_list, 0, sizeof (struct list_head));
+       new->port.xmit_buf = NULL;
+       new->port.client_data = NULL;
+       new->ctlp = NULL;
+       new->xmit_buf = NULL;
+       memset(&new->write_mtx.wait_list, 0, sizeof (struct list_head));
+       if (copy_to_user(argp, new, sizeof (struct r_port)))
+               ret = -EFAULT;
+       kfree(new);
+       return ret;
+}
+
 /*  IOCTL call handler into the driver */
 static int rp_ioctl(struct tty_struct *tty,
                    unsigned int cmd, unsigned long arg)
@@ -1284,8 +1312,7 @@ static int rp_ioctl(struct tty_struct *tty,
 
        switch (cmd) {
        case RCKP_GET_STRUCT:
-               if (copy_to_user(argp, info, sizeof (struct r_port)))
-                       ret = -EFAULT;
+               ret = get_struct(info, argp);
                break;
        case RCKP_GET_CONFIG:
                ret = get_config(info, argp);
-- 
2.11.0