smack: fix bug: SMACK64TRANSMUTE set on non-directory

When a new file system object is created
and the conditions for label transmutation are met,
the SMACK64TRANSMUTE extended attribute is set
on the object regardless of its type:
file, pipe, socket, symlink, or directory.

However,
SMACK64TRANSMUTE may only be set on directories.

This bug is a combined effect of the commits [1] and [2]
which both transfer functionality
from smack_d_instantiate() to smack_inode_init_security(),
but only in part.

Commit [1] set blank  SMACK64TRANSMUTE on improper object types.
Commit [2] set "TRUE" SMACK64TRANSMUTE on improper object types.

[1] 2023-06-10,
Fixes: baed456 ("smack: Set the SMACK64TRANSMUTE xattr in smack_inode_init_security()")
Link: https://lore.kernel.org/linux-security-module/20230610075738.3273764-3-roberto.sassu@huaweicloud.com/

[2] 2023-11-16,
Fixes: e63d86b ("smack: Initialize the in-memory inode in smack_inode_init_security()")
Link: https://lore.kernel.org/linux-security-module/20231116090125.187209-5-roberto.sassu@huaweicloud.com/

Signed-off-by: Konstantin Andreev <andreev@swemel.ru>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

Author: goongas

security/smack/smack_lsm.c

@@ -1027,18 +1027,20 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
 		if (!trans_cred)
 			issp->smk_inode = dsp;
 
-		issp->smk_flags |= SMK_INODE_TRANSMUTE;
-		xattr_transmute = lsm_get_xattr_slot(xattrs,
-						     xattr_count);
-		if (xattr_transmute) {
-			xattr_transmute->value = kmemdup(TRANS_TRUE,
-							 TRANS_TRUE_SIZE,
-							 GFP_NOFS);
-			if (!xattr_transmute->value)
-				return -ENOMEM;
-
-			xattr_transmute->value_len = TRANS_TRUE_SIZE;
-			xattr_transmute->name = XATTR_SMACK_TRANSMUTE;
+		if (S_ISDIR(inode->i_mode)) {
+			issp->smk_flags |= SMK_INODE_TRANSMUTE;
+			xattr_transmute = lsm_get_xattr_slot(xattrs,
+							     xattr_count);
+			if (xattr_transmute) {
+				xattr_transmute->value = kmemdup(TRANS_TRUE,
+								 TRANS_TRUE_SIZE,
+								 GFP_NOFS);
+				if (!xattr_transmute->value)
+					return -ENOMEM;
+
+				xattr_transmute->value_len = TRANS_TRUE_SIZE;
+				xattr_transmute->name = XATTR_SMACK_TRANSMUTE;
+			}
 		}
 	}