[PATCH 4.20 49/65] RDMA/iwcm: Dont copy past the end of dev_name() string

[Greg Kroah-Hartman]

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Steve Wise <swise@xxxxxxxxxxxxxxxxxxxxx>

commit d53ec8af56d5163f8a42e961ece3aeb5c560e79d upstream.

We now use dev_name(&ib_device->dev) instead of ib_device->name in iwpm
messages.  The name field in struct device is a const char *, where as
ib_device->name is a char array of size IB_DEVICE_NAME_MAX, and it is
pre-initialized to zeros.

Since iw_cm_map() was using memcpy() to copy in the device name, and
copying IWPM_DEVNAME_SIZE bytes, it ends up copying past the end of the
source device name string and copying random bytes.  This results in iwpmd
failing the REGISTER_PID request from iwcm.  Thus port mapping is broken.

Validate the device and if names, and use strncpy() to inialize the entire
message field.

Fixes: 896de0090a85 ("RDMA/core: Use dev_name instead of ibdev->name")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Steve Wise <swise@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/infiniband/core/iwcm.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/drivers/infiniband/core/iwcm.c
+++ b/drivers/infiniband/core/iwcm.c
@@ -502,17 +502,21 @@ static void iw_cm_check_wildcard(struct
  */
 static int iw_cm_map(struct iw_cm_id *cm_id, bool active)
 {
+	const char *devname = dev_name(&cm_id->device->dev);
+	const char *ifname = cm_id->device->iwcm->ifname;
 	struct iwpm_dev_data pm_reg_msg;
 	struct iwpm_sa_data pm_msg;
 	int status;
 
+	if (strlen(devname) >= sizeof(pm_reg_msg.dev_name) ||
+	    strlen(ifname) >= sizeof(pm_reg_msg.if_name))
+		return -EINVAL;
+
 	cm_id->m_local_addr = cm_id->local_addr;
 	cm_id->m_remote_addr = cm_id->remote_addr;
 
-	memcpy(pm_reg_msg.dev_name, dev_name(&cm_id->device->dev),
-	       sizeof(pm_reg_msg.dev_name));
-	memcpy(pm_reg_msg.if_name, cm_id->device->iwcm->ifname,
-	       sizeof(pm_reg_msg.if_name));
+	strncpy(pm_reg_msg.dev_name, devname, sizeof(pm_reg_msg.dev_name));
+	strncpy(pm_reg_msg.if_name, ifname, sizeof(pm_reg_msg.if_name));
 
 	if (iwpm_register_pid(&pm_reg_msg, RDMA_NL_IWCM) ||
 	    !iwpm_valid_pid())