[PATCH 4.9 110/175] Smack: Fix wrong semantics in smk_access_entry()

[Greg Kroah-Hartman]

From: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>

[ Upstream commit 6d14f5c7028eea70760df284057fe198ce7778dd ]

In the smk_access_entry() function, if no matching rule is found
in the rust_list, a negative error code will be used to perform bit
operations with the MAY_ enumeration value. This is semantically
wrong. This patch fixes this issue.

Signed-off-by: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>
Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 security/smack/smack_access.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c
index e5d5c7fb2dac..b25cc69ef7ba 100644
--- a/security/smack/smack_access.c
+++ b/security/smack/smack_access.c
@@ -90,23 +90,22 @@ int log_policy = SMACK_AUDIT_DENIED;
 int smk_access_entry(char *subject_label, char *object_label,
 			struct list_head *rule_list)
 {
-	int may = -ENOENT;
 	struct smack_rule *srp;
 
 	list_for_each_entry_rcu(srp, rule_list, list) {
 		if (srp->smk_object->smk_known == object_label &&
 		    srp->smk_subject->smk_known == subject_label) {
-			may = srp->smk_access;
-			break;
+			int may = srp->smk_access;
+			/*
+			 * MAY_WRITE implies MAY_LOCK.
+			 */
+			if ((may & MAY_WRITE) == MAY_WRITE)
+				may |= MAY_LOCK;
+			return may;
 		}
 	}
 
-	/*
-	 * MAY_WRITE implies MAY_LOCK.
-	 */
-	if ((may & MAY_WRITE) == MAY_WRITE)
-		may |= MAY_LOCK;
-	return may;
+	return -ENOENT;
 }
 
 /**
-- 
2.30.2