[PATCH v2 3/3] libsepol: assure string NUL-termination of ibdev_name

[Christian Göttsche <cgzones@xxxxxxxxxxxxxx>]

Clang complains:

    ibendport_record.c: In function ‘sepol_ibendport_get_ibdev_name’:
    ibendport_record.c:169:2: error: ‘strncpy’ specified bound 64 equals destination size [-Werror=stringop-truncation]
      169 |  strncpy(tmp_ibdev_name, ibendport->ibdev_name, IB_DEVICE_NAME_MAX);
          |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    ibendport_record.c: In function ‘sepol_ibendport_set_ibdev_name’:
    ibendport_record.c:189:2: error: ‘strncpy’ specified bound 64 equals destination size [-Werror=stringop-truncation]
      189 |  strncpy(tmp, ibdev_name, IB_DEVICE_NAME_MAX);
          |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

strncpy(3) does not NUL-terminate the destination if the source is of
the same length or longer then the specified size.
The source of these copies are retrieved from
sepol_ibendport_alloc_ibdev_name(), which allocates a fixed amount of
IB_DEVICE_NAME_MAX bytes.
Reduce the size to copy by 1 of all memory regions allocated by
sepol_ibendport_alloc_ibdev_name().

Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
---
v2:
  - use at all affected places as pointed out by James Carter

 libsepol/src/ibendport_record.c | 8 ++++----
 libsepol/src/ibendports.c       | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/libsepol/src/ibendport_record.c b/libsepol/src/ibendport_record.c
index adf67161..1eb50914 100644
--- a/libsepol/src/ibendport_record.c
+++ b/libsepol/src/ibendport_record.c
@@ -62,7 +62,7 @@ int sepol_ibendport_key_create(sepol_handle_t *handle,
 	if (sepol_ibendport_alloc_ibdev_name(handle, &tmp_key->ibdev_name) < 0)
 		goto err;
 
-	strncpy(tmp_key->ibdev_name, ibdev_name, IB_DEVICE_NAME_MAX);
+	strncpy(tmp_key->ibdev_name, ibdev_name, IB_DEVICE_NAME_MAX - 1);
 	tmp_key->port = port;
 
 	*key_ptr = tmp_key;
@@ -166,7 +166,7 @@ int sepol_ibendport_get_ibdev_name(sepol_handle_t *handle,
 	if (sepol_ibendport_alloc_ibdev_name(handle, &tmp_ibdev_name) < 0)
 		goto err;
 
-	strncpy(tmp_ibdev_name, ibendport->ibdev_name, IB_DEVICE_NAME_MAX);
+	strncpy(tmp_ibdev_name, ibendport->ibdev_name, IB_DEVICE_NAME_MAX - 1);
 	*ibdev_name = tmp_ibdev_name;
 	return STATUS_SUCCESS;
 
@@ -186,7 +186,7 @@ int sepol_ibendport_set_ibdev_name(sepol_handle_t *handle,
 	if (sepol_ibendport_alloc_ibdev_name(handle, &tmp) < 0)
 		goto err;
 
-	strncpy(tmp, ibdev_name, IB_DEVICE_NAME_MAX);
+	strncpy(tmp, ibdev_name, IB_DEVICE_NAME_MAX - 1);
 	free(ibendport->ibdev_name);
 	ibendport->ibdev_name = tmp;
 	return STATUS_SUCCESS;
@@ -230,7 +230,7 @@ int sepol_ibendport_clone(sepol_handle_t *handle,
 	if (sepol_ibendport_alloc_ibdev_name(handle, &new_ibendport->ibdev_name) < 0)
 		goto omem;
 
-	strncpy(new_ibendport->ibdev_name, ibendport->ibdev_name, IB_DEVICE_NAME_MAX);
+	strncpy(new_ibendport->ibdev_name, ibendport->ibdev_name, IB_DEVICE_NAME_MAX - 1);
 	new_ibendport->port = ibendport->port;
 
 	if (ibendport->con &&
diff --git a/libsepol/src/ibendports.c b/libsepol/src/ibendports.c
index 6d56c9a1..ee5cb193 100644
--- a/libsepol/src/ibendports.c
+++ b/libsepol/src/ibendports.c
@@ -34,7 +34,7 @@ static int ibendport_from_record(sepol_handle_t *handle,
 					   &ibdev_name) < 0)
 		goto err;
 
-	strncpy(tmp_ibendport->u.ibendport.dev_name, ibdev_name, IB_DEVICE_NAME_MAX);
+	strncpy(tmp_ibendport->u.ibendport.dev_name, ibdev_name, IB_DEVICE_NAME_MAX - 1);
 
 	free(ibdev_name);
 	ibdev_name = NULL;
-- 
2.32.0