[PATCH for 4.19.y 2/3] smack: Retrieve transmuting information in smack_inode_getsecurity()

[Munehisa Kamata <kamatam@amazon.com>]

From: Roberto Sassu <roberto.sassu@huawei.com>

commit 3a3d8fce31a49363cc31880dce5e3b0617c9c38b upstream.

Enhance smack_inode_getsecurity() to retrieve the value for
SMACK64TRANSMUTE from the inode security blob, similarly to SMACK64.

This helps to display accurate values in the situation where the security
labels come from mount options and not from xattrs.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
[4.19: adjusted for the lack of helper functions]
Fixes: d6d80cb57be4 ("Smack: Base support for overlayfs")
Signed-off-by: Munehisa Kamata <kamatam@amazon.com>
---
 security/smack/smack_lsm.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index a09a9c6bbdf6..db729834d8ba 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1490,10 +1490,19 @@ static int smack_inode_getsecurity(struct inode *inode,
 	struct super_block *sbp;
 	struct inode *ip = (struct inode *)inode;
 	struct smack_known *isp;
+	struct inode_smack *ispp;
+	size_t label_len;
+	char *label = NULL;
 
-	if (strcmp(name, XATTR_SMACK_SUFFIX) == 0)
+	if (strcmp(name, XATTR_SMACK_SUFFIX) == 0) {
 		isp = smk_of_inode(inode);
-	else {
+	} else if (strcmp(name, XATTR_SMACK_TRANSMUTE) == 0) {
+		ispp = inode->i_security;
+		if (ispp->smk_flags & SMK_INODE_TRANSMUTE)
+			label = TRANS_TRUE;
+		else
+			label = "";
+	} else {
 		/*
 		 * The rest of the Smack xattrs are only on sockets.
 		 */
@@ -1515,13 +1524,18 @@ static int smack_inode_getsecurity(struct inode *inode,
 			return -EOPNOTSUPP;
 	}
 
+	if (!label)
+		label = isp->smk_known;
+
+	label_len = strlen(label);
+
 	if (alloc) {
-		*buffer = kstrdup(isp->smk_known, GFP_KERNEL);
+		*buffer = kstrdup(label, GFP_KERNEL);
 		if (*buffer == NULL)
 			return -ENOMEM;
 	}
 
-	return strlen(isp->smk_known);
+	return label_len;
 }
 
 
-- 
2.34.1