From: "Yan, Zheng" <zyan@redhat.com>
Date: Mon, 11 Sep 2017 12:10:08 +0800
Subject: ceph: avoid panic in create_session_open_msg() if utsname() returns
 NULL
Git-commit: 717e6f2893eb35ce6728c3cacdc297b78d371b31
Patch-mainline: v4.14-rc2
References: FATE#324714

utsname() can return NULL while process is exiting. Kernel releases
file locks during process exits. We send request to mds when releasing
file lock. So it's possible that we open mds session while process is
exiting. utsname() is called in create_session_open_msg().

Link: http://tracker.ceph.com/issues/21275
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
[idryomov@gmail.com: drop utsname.h include from mds_client.c]
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Acked-by: Luis Henriques <lhenriques@suse.com>
---
 fs/ceph/mds_client.c | 7 ++++---
 fs/ceph/mds_client.h | 3 +++
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 9dd6b836ac9e..84edfc60d87a 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -7,7 +7,6 @@
 #include <linux/sched.h>
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
-#include <linux/utsname.h>
 #include <linux/ratelimit.h>
 
 #include "super.h"
@@ -884,8 +883,8 @@ static struct ceph_msg *create_session_open_msg(struct ceph_mds_client *mdsc, u6
 	void *p;
 
 	const char* metadata[][2] = {
-		{"hostname", utsname()->nodename},
-		{"kernel_version", utsname()->release},
+		{"hostname", mdsc->nodename},
+		{"kernel_version", init_utsname()->release},
 		{"entity_id", opt->name ? : ""},
 		{"root", fsopt->server_path ? : "/"},
 		{NULL, NULL}
@@ -3539,6 +3538,8 @@ int ceph_mdsc_init(struct ceph_fs_client *fsc)
 	init_rwsem(&mdsc->pool_perm_rwsem);
 	mdsc->pool_perm_tree = RB_ROOT;
 
+	strncpy(mdsc->nodename, utsname()->nodename,
+		sizeof(mdsc->nodename) - 1);
 	return 0;
 }
 
diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index db57ae98ed34..636d6b2ec49c 100644
--- a/fs/ceph/mds_client.h
+++ b/fs/ceph/mds_client.h
@@ -8,6 +8,7 @@
 #include <linux/rbtree.h>
 #include <linux/spinlock.h>
 #include <linux/refcount.h>
+#include <linux/utsname.h>
 
 #include <linux/ceph/types.h>
 #include <linux/ceph/messenger.h>
@@ -368,6 +369,8 @@ struct ceph_mds_client {
 
 	struct rw_semaphore     pool_perm_rwsem;
 	struct rb_root		pool_perm_tree;
+
+	char nodename[__NEW_UTS_LEN + 1];
 };
 
 extern const char *ceph_mds_op_name(int op);