smack: fix logic in smack_inode_init_security function

In principle if this function was called with "value" == NULL and "len"
not NULL it could return different results for the "len" compared to a
case where "name" was not NULL. This is a hypothetical case that does
not exist in the kernel, but it's a logic bug nonetheless.
Signed-off-by: Lukasz Pawelczyk <l.pawelczyk@samsung.com>

security/smack/smack_lsm.c

@@ -800,7 +800,7 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
 	if (name)
 		*name = XATTR_SMACK_SUFFIX;
 
-	if (value) {
+	if (value && len) {
 		rcu_read_lock();
 		may = smk_access_entry(skp->smk_known, dsp->smk_known,
 				       &skp->smk_rules);
@@ -821,10 +821,9 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
 		*value = kstrdup(isp->smk_known, GFP_NOFS);
 		if (*value == NULL)
 			return -ENOMEM;
-	}
 
-	if (len)
 		*len = strlen(isp->smk_known);
+	}
 
 	return 0;
 }