linux-kernel - [RFC][PATCH 3/5] smack: Always determine inode labels in smack_inode_init

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Message-Id: <20230607123612.2791303-4-roberto.sassu@huaweicloud.com>
Date:   Wed,  7 Jun 2023 14:36:10 +0200
From:   Roberto Sassu <roberto.sassu@...weicloud.com>
To:     casey@...aufler-ca.com, paul@...l-moore.com, jmorris@...ei.org,
        serge@...lyn.com
Cc:     linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: [RFC][PATCH 3/5] smack: Always determine inode labels in smack_inode_init_security()

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

The inode_init_security hook is already a good place to initialize the
in-memory inode. And that is also what SELinux does.

In preparation for this, move the existing smack_inode_init_security() code
outside the 'if (xattr)' condition, and set the xattr, if provided.

This change does not have any impact on the current code, since every time
security_inode_init_security() is called, the initxattr() callback is
passed and, thus, xattr is non-NULL.

Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
---
 security/smack/smack_lsm.c | 78 +++++++++++++++++++-------------------
 1 file changed, 40 insertions(+), 38 deletions(-)

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 162ca400f07..f7382448e12 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -948,49 +948,51 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
 	struct xattr *xattr = lsm_get_xattr_slot(xattrs, xattr_count);
 	int may;
 
-	if (xattr) {
-		/*
-		 * If equal, transmuting already occurred in
-		 * smack_dentry_create_files_as(). No need to check again.
-		 */
-		if (tsp->smk_task != tsp->smk_transmuted) {
-			rcu_read_lock();
-			may = smk_access_entry(skp->smk_known, dsp->smk_known,
-					       &skp->smk_rules);
-			rcu_read_unlock();
-		}
+	/*
+	 * If equal, transmuting already occurred in
+	 * smack_dentry_create_files_as(). No need to check again.
+	 */
+	if (tsp->smk_task != tsp->smk_transmuted) {
+		rcu_read_lock();
+		may = smk_access_entry(skp->smk_known, dsp->smk_known,
+				       &skp->smk_rules);
+		rcu_read_unlock();
+	}
+
+	/*
+	 * In addition to having smk_task equal to smk_transmuted,
+	 * if the access rule allows transmutation and the directory
+	 * requests transmutation then by all means transmute.
+	 * Mark the inode as changed.
+	 */
+	if ((tsp->smk_task == tsp->smk_transmuted) ||
+	    (may > 0 && ((may & MAY_TRANSMUTE) != 0) &&
+	     smk_inode_transmutable(dir))) {
+		struct xattr *xattr_transmute;
 
 		/*
-		 * In addition to having smk_task equal to smk_transmuted,
-		 * if the access rule allows transmutation and the directory
-		 * requests transmutation then by all means transmute.
-		 * Mark the inode as changed.
+		 * The caller of smack_dentry_create_files_as()
+		 * should have overridden the current cred, so the
+		 * inode label was already set correctly in
+		 * smack_inode_alloc_security().
 		 */
-		if ((tsp->smk_task == tsp->smk_transmuted) ||
-		    (may > 0 && ((may & MAY_TRANSMUTE) != 0) &&
-		     smk_inode_transmutable(dir))) {
-			struct xattr *xattr_transmute;
-
-			/*
-			 * The caller of smack_dentry_create_files_as()
-			 * should have overridden the current cred, so the
-			 * inode label was already set correctly in
-			 * smack_inode_alloc_security().
-			 */
-			if (tsp->smk_task != tsp->smk_transmuted)
-				isp = dsp;
-			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 == NULL)
-					return -ENOMEM;
-
-				xattr_transmute->value_len = TRANS_TRUE_SIZE;
-				xattr_transmute->name = XATTR_SMACK_TRANSMUTE;
-			}
+		if (tsp->smk_task != tsp->smk_transmuted)
+			isp = dsp;
+
+		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 == NULL)
+				return -ENOMEM;
+
+			xattr_transmute->value_len = TRANS_TRUE_SIZE;
+			xattr_transmute->name = XATTR_SMACK_TRANSMUTE;
 		}
+	}
 
+	if (xattr) {
 		xattr->value = kstrdup(isp->smk_known, GFP_NOFS);
 		if (xattr->value == NULL)
 			return -ENOMEM;
-- 
2.25.1