net/sunrpc: fix reference count leaks in rpc_sysfs_xprt_state_change

jira LE-1907
cve CVE-2021-47624
Rebuild_History Non-Buildable kernel-4.18.0-553.16.1.el8_10
commit-author Xiyu Yang <xiyuyang19@fudan.edu.cn>
commit 776d794

The refcount leak issues take place in an error handling path. When the
3rd argument buf doesn't match with "offline", "online" or "remove", the
function simply returns -EINVAL and forgets to decrease the reference
count of a rpc_xprt object and a rpc_xprt_switch object increased by
rpc_sysfs_xprt_kobj_get_xprt() and
rpc_sysfs_xprt_kobj_get_xprt_switch(), causing reference count leaks of
both unused objects.

Fix this issue by jumping to the error handling path labelled with
out_put when buf matches none of "offline", "online" or "remove".

	Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
	Signed-off-by: Xin Xiong <xiongx18@fudan.edu.cn>
	Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
	Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
(cherry picked from commit 776d794)
	Signed-off-by: Jonathan Maple <jmaple@ciq.com>

Author: PlaidCat

net/sunrpc/sysfs.c

@@ -299,8 +299,10 @@ static ssize_t rpc_sysfs_xprt_state_change(struct kobject *kobj,
 		online = 1;
 	else if (!strncmp(buf, "remove", 6))
 		remove = 1;
-	else
-		return -EINVAL;
+	else {
+		count = -EINVAL;
+		goto out_put;
+	}
 
 	if (wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_KILLABLE)) {
 		count = -EINTR;