In sysfs_check_holders func, table_name is obtained by calling
dm_mapname func, and then call dm_reassign_table for reassigning
table. However, we donnot check whether dm_mapname func returns
NULL, and then it may cause a segmentation fault in dm_task_set_name.

Here, we will check whether dm_mapname func returns NULL before
using it.

Signed-off-by: Zhiqiang Liu <liuzhiqian...@huawei.com>
Signed-off-by: Lixiaokeng <lixiaok...@huawei.com>
---
 libmultipath/sysfs.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/libmultipath/sysfs.c b/libmultipath/sysfs.c
index 12a82d95..5390de62 100644
--- a/libmultipath/sysfs.c
+++ b/libmultipath/sysfs.c
@@ -278,7 +278,11 @@ int sysfs_check_holders(char * check_devt, char * new_devt)
                        continue;
                }
                table_name = dm_mapname(major, table_minor);
-
+               if (!table_name) {
+                       condlog(2, "%s: mapname not found for %d:%d", check_dev,
+                               major, table_minor);
+                       continue;
+               }
                condlog(0, "%s: reassign table %s old %s new %s", check_dev,
                        table_name, check_devt, new_devt);

-- 

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