From: Leon Romanovsky <leonro@mellanox.com>
Date: Tue, 19 Feb 2019 13:09:57 +0200
Subject: RDMA/iwcm: Fix string truncation error
Patch-mainline: v5.1-rc1
Git-commit: 1882ab867863531ab9caab81fd6ac5fee6d1a314
References: bsc#1103992 FATE#326009

The strlen() check at the beginning of iw_cm_map() ensures that devname
and ifname strings are less than destinations to which they are supposed
to be copied. Change strncpy() call to be strcpy(), because we are
protected from overflow. Zero the entire string buffer to avoid copying
uninitialized kernel stack memory to userspace.

This fixes the compilation warning below:

In file included from ./include/linux/dma-mapping.h:6,
                 from drivers/infiniband/core/iwcm.c:38:
In function _strncpy_,
    inlined from _iw_cm_map_ at drivers/infiniband/core/iwcm.c:519:2:
./include/linux/string.h:253:9: warning: ___builtin_strncpy_ specified
bound 32 equals destination size [-Wstringop-truncation]
  return __builtin_strncpy(p, q, size);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fixes: d53ec8af56d5 ("RDMA/iwcm: Don't copy past the end of dev_name() string")
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/infiniband/core/iwcm.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/infiniband/core/iwcm.c
+++ b/drivers/infiniband/core/iwcm.c
@@ -504,7 +504,7 @@ static int iw_cm_map(struct iw_cm_id *cm
 {
 	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_dev_data pm_reg_msg = {};
 	struct iwpm_sa_data pm_msg;
 	int status;
 
@@ -515,8 +515,8 @@ static int iw_cm_map(struct iw_cm_id *cm
 	cm_id->m_local_addr = cm_id->local_addr;
 	cm_id->m_remote_addr = cm_id->remote_addr;
 
-	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));
+	strcpy(pm_reg_msg.dev_name, devname);
+	strcpy(pm_reg_msg.if_name, ifname);
 
 	if (iwpm_register_pid(&pm_reg_msg, RDMA_NL_IWCM) ||
 	    !iwpm_valid_pid())